Can't speak for anyone else, but I came at it with what I would like D&D to be like, then thought about what mechanics fit that and that is when I wrote those down.
That most of these exist in some TTRPGs and I happen to know / mention them for some does not mean that I want D&D to be more like that game specifically, only that the game has some features I prefer over how D&D does the same / a similar thing. That something similar exists in some other TTRPG should also not be a surprise...
Take the broader subclasses for example, you can accomplish this by having different feats / skills to select from, and having skill chains. Add to this the desire for progression to be synchronized and the two-tiered subclass approach from Shadow of the Weird Wizard looks like a great way to do this in a way that is familiar to players of D&D and accomplishes basically all of it in a very flexible manner. So in the context of D&D, I think the SotWW approach is probably the right one to go with if the end goal is what I wanted in the first place.
Or take the combat with no attack rolls and tiers of success, I want combat to be sped up and more interesting that just 'you miss, you do 6 damage, you do 9 damage, ...' tiers speed it up and they can allow for more interesting results than rolling 1d8 to determine the damage ever would. I also like the mechanics to be the same for melee and casters, this accomplishes that too.
In summary, what I describe is my platonic ideal for D&D, not an unholy mix of D&D and two or so other games I wish it would be like more.