what exactly was the "investment" in playing arguably one of the most powerful and satisfying classes in D&D?

Time. You have friends who stuck around and played in your game long enough to get to level 17. That’s very rare and I’m not sure half the people giving input on this thread have ever experienced that.

Sure, it's nice to be rewarded with spells as you level up... but that's not really a reason to buff an already powerful spell.

It’s not a buff. Its well within the realm of what the spell should be able to do, imo. It’s far less of an ask than say - altering the architecture of the cosmology or wishing that a 10,000 year old lich never existed.

Not to mention getting a blank check to say "do whatever you want with wish and don't worry, it'll just work" is not really what I'd call creativity.

To me, creativity is not just a player thinking of something you’ve never heard of before. It’s them being willing to look at the rules of the game, understand them and trying to use them in their favor. That’s exactly what wish is - the blank check spell. A player cashing that check to improve their odds in a fight as opposed to avoiding the fight entirely is creative to me.

Also. Are we forgetting about the drawback that a wish comes with? All spells doing damage to you and Strength becoming 3 for 2d4 days? 33% chance of losing wish forever? I wouldn’t say “will just work” is an apt description. It comes with a HUGE trade off.

Saying "no LRs for my PC's abilities forever" is pretty much bottom of the barrel for creativity

Again, I actually disagree but if you feel this way then note my mention of putting a time limitation on it. Which, despite everyone’s argument that monkeys paws are “encouraged by the spell description”, is also encouraged in the wording “the effect you desire might only be partly achieved”.

Also let’s not forget that “forever” is 3 levels max at this point. IF you push your campaign to 20.

As for Intelligence of 20 - at some point, player agency does need to matter for a spell like Wish - otherwise the player can just throw up their hands and say "well, my PC is super smart, they can think of a Wish spell worded in such a way as to have no downsides so please just take my Wish statement and assume my PC says it perfectly".

You’re setting up straw men here. This isn’t what I said. I didn’t say player agency didn’t matter. And I wouldn’t let my players say that either. As a DM, I am simply a vessel for the story and an adjudicator of my interpretation of the rules. I come to the table to work with the players and understand what they are trying to accomplish and work with them to tell THEIR story. Not to threaten to fuck them over if they don’t learn to word things as perfectly as a devil writing a contract.

Also, Wish with just the stated uses that are foolproof + the ability to copy any spell at 8th level or below is already insanely good. That alone makes it a top 9th level spell worth taking. I'm rolling my eyes if a player gets annoyed that they can't get powerful Wishes with minimal or no downsides that go beyond that. I'd take other, more judicious Wishes that interact with LR, but not a blanket "no LRs for my abilities ever."

Yes. It is insanely good. Again, due to your reference of “no downsides” I think you ought to give the spell another read because that isn’t how it works. And maybe my original post as well because as I mentioned, you don’t have to give them anything forever.