After trying and failing at a whole bunch of experimental shit over the past year-ish (which might become a slush pile at some point), my regular homegame players and I gave up. We went back to 5e, which we're all extremely familiar with and thus need to spend a minimal amount of time dicking around with.
Here's how I run it.
1. Use E5.
E5, a variation of the venerable E6 from the 3.5 days, is a version of 5e that stops leveling at level 5. In E5, you stop leveling up at level 5, but every level thereafter gets you a new feat.
It's really good. It makes a lot of 5e's design decisions make a lot more sense. It makes all the random feats that seem kinda cool but you can never really afford suddenly viable. It makes all the "you get one 1st level and one 2nd level spell extra per day" feats useful. It makes Sharpshooter and GWM a lot costlier, since your proficiency bonus never really gets above +3. It allows for a smidgen of build-crafting but keeps a firm lid on power level.
It's good. If I could only make one change to 5e, I think this'd be it.
2. Use Extended Rests.
Extended Rests, aka "Gritty Realism," is a controversial-ish alternate rule from the DMG. It makes short rests 8 hours (one night's sleep) and makes long rests 3 days.
Much ink has been spilled over this, but I think it's basically good. On a practical level, it effectively means that players can only reliably long rest in a safe place, and can only short rest outside the dungeon. It makes them more cautious, more wary. It's a really good way to preserve some of the light shows of 5e but slow down the timeline. It also makes feats and perks that let you heal more on short rests really good, and provides a (much-needed, imo) buff to the short-rest classes like Fighter, Monk, and Warlock.
You'll also want to extend the duration on spells: anything that used to take 10 minutes or more gets kicked up one "time class." 10 minute spells become 1 hour, 1 hour spells become 8 hours, 8 hours becomes 1 day, 1 day becomes 1 week, and so on. 1 minute and instantaneous spells don't change, because those are "single-combat spells" and combat pace hasn't changed.
My players hated it at first but now have gotten used to it. It's good.
3. Cut damage cantrips from every class except Sorcerer.
No firebolt. No toll the dead. No vicious mockery. No fucking eldritch blast.
Suddenly, all your casters suddenly have to use their brains in combat. Suddenly, all your casters might consider putting points into something other than their main stat. Suddenly, Sorcerers actually feel cool and unique and special because they get to shoot lightning out of their fucking hands whenever they want.
My players almost rioted when I first dropped this on them, but from my view it's an extremely good change. They still get cantrips, they can even still use those cantrips in combat (minor illusion remains very good), but there's suddenly no default action for casters.
It also helps make damage actually matter. A Fighter or Barbarian who can reliably get 20+ damage off per round is actually very, very helpful, because your casters will need to actually commit to get damage numbers that high.
It makes your martials feel cooler, it makes Sorcerers feel cooler, it makes everybody actually think about combat a little more. It's the most controversial thing here but also very good.
4. A million other tiny tweaks that are basically unnecessary but I added anyways.
Here's an incomplete list:
- Strip ASIs out of species and attach them to backgrounds instead. (Apparently 5.5 is doing this, but I thought of it first.)
- Use inventory slots. Most items take 1, big weapons take 2 or 3 or 4. Armor takes slots equal to AC - 10. You get slots equal to STR score + CON score.
- Add a dismemberment table they roll on whenever they reach 0HP. If they roll above a 10 (higher is deadlier), they automatically fail one death save.
- Every time they would take 1 exhaustion level, fill 1d6 inventory slots with "exhaustion slots" instead. You clear [HD roll] exhaustion slots per short rest, and all exhaustion slots on a long rest.
- Fuck the common tongue. Use my gigantic language chart instead. You start with languages equal to INT score / 5, rounding down. Backgrounds and classes still grant bonus languages, as normal. (Someday I'll make this into a flowchart poster that you can buy.)
- Replace all the non-resistance related stuff from the Barbarian's rage with a flat STR bonus, starting from +4 and ending at +8.
- Let Barbarians spend one use of rage to negate 1d6 inventory slots of exhaustion.
- Give all Barbarians the features of the Berserker Path on top of whatever else they get. These features should be core Barbarian features.
- Give all Bards the features of the College of Lore on top of whatever else they get. These features should be core Bard features.
- Cut guidance.
- Cut the bit from Wild Shape that says "all your clothes and gear transform with you." Let your Druids be direwolves with their swords in the mouths, but then have to be naked afterwards.
- Let Land Druids change their chosen Land once every full moon.
- Let Fighters use Second Wind while they're unconscious.
- Give all Fighters the features of the Battlemaster. Figure out which subclasses get which maneuvers as you need them.
- Let Eldritch Knights and Arcane Tricksters choose two magic schools of four to get their spells from (EK: Abjuration, Conjuration, Evocation, Transmutation // AT: Divination, Enchantment, Illusion, Transmutation).
- Give all Monks the Open Hand Technique feature at level 2.
- Give Open Hand monks a feature called "Thousand Steps" that lets them add their proficiency bonus to their AC against one attack as a reaction, then rename the subclass to "Way of the Mountaintop."
- Give Four Elements Monks control flame, gust, mold earth, and shape water at levels 3, 6, 11, and 17, in any order they choose.
- Make Divine Sense an always-on passive for Paladins.
- Use the revised rules from Tasha's for Rangers.
- Let Thief Rogues use DEX in place of STR to determine their inventory size.
- Give all Sorcerers the features of Wild Magic on top of whatever else they get. These features should be core Sorcerer features.
- Give Sorcerers an extra Metamagic at level 6.
- On the Wild Magic table, change basically any entry that says "1 minute" to "1d6 hours" or "1d6 days." Cut any line that says anything like "it [disappears/reverts to normal/returns] after 1 minute." Let Sorcerers actually be fucking weird.
- Give Sorcerers chaos bolt for free.
- Attach the Hexblade feature that allows you to use CHA for attacks with your sword to Pact of the Blade instead of Hexblade (they'll be fine without anything to compensate).
- Add an invocation called "Fell Legions" for Blade Pact Warlocks that gives proficiency in medium armor and shields.
- Any invocation that essentially expand your spell list (Bewitching Whispers, Dreadful Word, etc.) now provide one free casting of the spell per short rest.
- Cut prepared spells from Wizards, they can just cast any spell from their spellbook. Only give them 1 free spell per level, rather than 2.
- Add a line to the Grappler feat that lets you grapple a target 1 size larger than normal, and you deal 1d4 bonus damage to targets you're grappling.
- Make light and dancing lights 1st level spells instead of cantrips.
- When combat starts, PCs roll initiative trying to beat [10 + enemy DEX mod]. If they succeed, they go first; if they fail, they go after the monsters.
5. Move fast and break things.
Stop caring about balance. Make lots of rulings. Tweak and modify the game rules even further. Use OSR monsters stat blocks. Play fast and loose.
This is, obviously, just how I roll. There are lots of other ways to do it. But my players are now basically on board with basically all of these, and our game actually feels like D&D instead of... whatever 5e normally feels like.