I think it's within the scope still to make the game enough like D&D.
Mostly it has to do with stuff like...
- make Long Rest more restricted so it's actually a meaningful choice instead of a free ability and spell reset button
- nerf Jump height to 5e standards and add climbing as the main way to reach elevation This is VERY important from a tactical point of view. Climbing should halve your movement and Athletics and Acrobatics need to matter. Terrain should be much more than just giving you a +2/-2 to attack.
- revert Shove and Hide to Actions, give Rogues their unique abilities back
- nerf Shove distance to 5e standards so combat doesn't turn into a ridiculous shove fest
- fix Wizards leaning other classes spells and every class using scrolls (and before anyone says it's more fun this way... that's what multiclassing is for and we don't have it yet)
- add saving throws to homebrew stuff like surfaces and bombs and whatnot, no inescapable damage
