The diversity isn't dead, it's just that the groups you described created competitive environments that are not compatible with what you want to do. That speaks to the people you play with, not the game itself. Everyone makes their choice on how to approach the game.
So... from what I'm gathering... you want every piece of interaction, card filtering, card advantage, and mana advantage to be so grossly inefficient and/or niche that which one you use (or whether you even use them) doesn't make a meaningful impact on your win/loss record. Am I finally getting this right?
Don't use stupid hyperbole. We don't need sol ring or mana crypt or mana vault in this format. We don't need one mana tutors. We don't need cards like mystic remora or necropotence drawing cards at rates that have clearly been dubbed obscene.
Cutting these cards can suddenly open up room for synergy to actually compete, but no synergy will ever outclass a sol ring level card.
No, it wouldn't. Getting rid of those card will just have other cards who do the exact same things take their place.
Really, the only effect I could see happening is killing the diversity of the game. A lot of people like the fact that EDH can be super casual, super competitive or something in between. That they can build decks that are meant for certain levels of play and have the card pools to do that.
Honestly, man, not come off as hostile, but it really just sounds like you want everyone to play at a certain level because you think it's fun. You want everyone to conform to your definition of a good time under the guise that it will make the game better. Not too mention, your stance basically treats it like everyone plays at the cEDH level when that couldn't be further from the truth.
Not too mention that the measures you talk about would kill deck development. I pretty sure there are people out there who love upgrading their decks over time. Slowly but steadily phasing old cards and replacing them with better ones. The thrill of getting to play a deck that gets better and more efficient with time, tweaking and, yes, straight upgrades.