Would that not suit your purposes better than options for a basic system that has issues for you?
Possibly. However, in thirty years of gaming, there are only three systems where I don't have major issues with the basic system: Savage Worlds, Mutants and Masterminds 2e, and True20.
Savage Worlds, which I just discovered last year, is my go to game for non-supers. It edged out True20 by being non-class/level based. I do have a couple of quibbles with certain skills being too broad and see Gamble as unnecessary, but so far that has been the only complaint
True20 Revised is my d20 class/level of choice. However, I have an issue with the power system (wish it used skill points like Psychic's Handbook which was the basis) and a couple of feats are a little fiddly.
Mutants and Masterminds 2e: like True20 a couple of feats are too fiddly or my tastes.
So, basically, I have issues with most rpg systems including D&D 3e in which 90%of my pre-3e questionarie wants were implemented
With 3e my issues were
1. Level Drain
2. XP costs for casting certain spells and creating items
3. The power disaparity at higher levels between casters and non-casters (Well, I was never a fan of high level play anyway)
4. too many absolutes
5. non-biolgical aspects of race were still part of the write-up
6. mutliclassing
a. training is a variant not a default
b. allows players to circumvent the feats for armor proficiencies, weapon proficiencies, and at least one of the save feat
7. Clerics:
a. deity's domains not playing more of a role in shaping a divne character's spell list by default (the DMG had variant for DM tailoring spell lists).
b. not being a spontaneous caster
c. Save progression based on class rather than the deity served
d. Armor proficiency based on class rather than the deity served
e. power boosted to be more attractive
8. Druid
a. Animal Companion
b. Wild Shape
9. Monks not having the same level of customization as a fighter
10. Wizard
a. many of the balancing mechanisms were removed, neutered, or made a DMG variant
b. Specialist wizards with bonus spells rather than using some of the better options from 2e supplements.
11. System Mastery built into feats
12. No Hero Point option in core
13. Vancian Magic
14. issues with various spells
15. "Christmas Tree"
16. No ritual magic until Unearthed Arcana
17. much of the new PHB equipment
18. WOTC Supplements
a. Too much focus on Prestige classes rather than the PHB character customization until 3.5 and Unearthed Arcana and the Cityscape enhancement for wilderness/urban skill trade offs.
b. The race and class book format (which is still an issue for me with 4e).
c. The implementation of new classes, prestiges, and mechanics
My solution was to house rule (as I have done with nearly every rpg going back to AD&D 1e), incorporate some of the DMG variants, variants from Unearthed Arcana, and some third party products to shape the game.
4e fixes several of my issues, but introduces new ones or implements some fixes in a manner I do not like. There is very much a push/pull reaction when I look at it. Several people I know feel the same way. Or as one person, recently, phrased it, 3e was a toolbox. The DM was encouraged to modify and shape the game and given tools to do it. 4e more or less tells you to play a certain way, because it doesn't give you the options to change specific parts of the system.
Based on my own experience over the years, I think returning to the toolbox might be more useful.