Personally, I would argue that D&D is actually pretty restrictive--and 5e is a lot less open than many people think. I've heard from plenty of people who find it deeply frustrating for both classic old-school gaming (it largely defangs survival and logistics, it's much too high-magic, the extreme fragility of the first couple of levels fades too quickly, characters grow too fast, gold is plentiful but lacks for effective things to spend it on unless the DM invents stuff mostly from whole cloth, etc.) and more contemporary styles too.
I find that very curious. How would you describe that playstyle?
That's all well and good--for you. The bigger problem is that this isn't nearly as true for several other playstyles. For example, folks whose playstyle relies on the survival-and-logistics stuff, or folks looking for "story now" play, or folks wanting well-tested game balance so that they feel reasonably challenged but not punished by BS.
Contrary position: D&D should provide multiple different options that are all well-developed and full-throated, so that different groups can develop their preferred playstyle within that space. Instead of moving toward absolute smoothness and unobjectionable non-commitment, move toward commitment to multiple distinct flavors that are actually well-developed.
This really isn't nearly as hard as many folks like to characterize it. It's still a challenging task (any well-made game design should be at least somewhat challenging to make!), but it's quite achievable. A rigorously balanced (which DOES NOT MEAN absolute diamond-perfect 1:1 parity on everything, for God's sake!!!) combat and skill system core, with 13A-style "Nastier Specials" rules for DMs that want to play on the wild side or spice up their encounters. Rules that iterate on 4e's Skill Challenges, which act as an optional structure for non-combat encounters to help make them more textured, rather than being so purely "DM says"-driven if that's what the group wants. "Novice level" rules plus 13A-style "incremental advance" rules, alongside a separate but complementary gritty-survival rules module (that curtails over-use of magic to obviate survival/logistics challenges). Page 42-style "here's how to give meaningful rewards for improvised actions" rules, alongside useful reference tables for common world-elements and how they would be expressed in the rules, such as skill DCs for various actions/materials/etc., methods for developing reasonable and cohesive communities or geographic regions, and comprehensive advice on how to run the world as something self-consistent and rational, a set of rules to be puzzled out to their logical conclusions (and how to address it if you run into a logical conflict with something you've developed.) Maybe, if there's space, some text about different approaches to roleplay and what the rules both can and cannot do with regard to those approaches (e.g. the place of "reskinning" things).
This would easily cover the vast majority of preferred playstyles. Folks who want a grim-and-gritty game where you grub for every single advantage because the rules are always against you until you bend them to your will have Nastier Specials, Novice levels, incremental advances, and the survival module. Folks who want high-flying awesome narrative action heroics have the rigorous core, skill challenges, improvisation rules, and (possibly) the roleplay-and-rules advice. Folks looking for simulationist puzzle-solving have a robust skill system, world-development rules, and advice on how to address issues when established patterns produce problematic results.
Add in some examples of "legacy" rules (such as GP=XP) as opt-in stuff, and you're pretty much golden.
Now, of course, I've just described a TON of design work. That's...sort of the point. You're designing a game system. It's going to be an effort, and it's going to require a hell of a lot of testing and refinement. But it's entirely achievable, especially by the biggest names in the business.
