Part of the DM's side of the social contract is to adapt and improvise to players' choices. The DM already does that when the players go different ways than the DM expected. The players already have to adapt when the DM changes things up on them in the name of "story". The DM has a responsibility to do the same. Players respeccing is not "Forcing" the DM to do something any more than it would be the DM's campaign path forcing the Players to adapt to changes as well.I'd say the problem is rather about the social contract while playing the game, and about the perception people have even before the play.
You explained what you enjoy. I enjoy something different: I like RPGs when they make me think AND choose, including at character build and level-up. And yes that also means that I like when I have to pay the cost of those choices (example: I like the idea that if I design a Fighter specialized with swords, I might find a fanstastic magic axe and then I have to choose between using all my bonuses with a non-magic sword VS using the magic axe without bonuses; similarly, I'd rather play a Ranger that is much better in one environment than another, so I'll have a difference experience in the two cases). I do not get joy from a rule that removes the value of choices with a switch. At that point, I'd rather have a Ranger that is always good everywhere, than a farce where the Ranger could switch their favourite terrain on a night's sleep, and I'll be looking at other areas of the game to find meaningful choices. Let's agree to disagree what is fun for us. The question might be: could we still play at the same table?
So back to the problem, for me it is the fact that WotC is generally following a trend (started with Tasha) of making the game more and more casual and care-free compared to what I want to play. It might be surprising, because nowadays I mostly play with casual gamers, not hardcore D&D fans. And casual gamers never ask for this sort of facilitations, it seems to me that it is always hardcore fans on internet forums who seem to want the game easier and easier. IMXP newbies and casuals are a lot more intrigued by the game when it is taken seriously, challenging, and why not even a bit complicated (after all, these were the things that brought me into D&D a long time ago).
I said it is mainly about social contract and perceptions. From you words, I get that you are very scared of ending up with a DM that "forces you to play something unfun". But my perception is the opposite, that if you were playing with me, it would be you forcing me (the DM) to run a game that is unfun to run, by keep changing your PC to adapt to new challenges and then significantly decrease their importance or variety. OTOH, as a DM I know I have always allowed a player to "respec" their PC if they were unhappy. Not having respec rules allowed me to deal directly with the player, so everyone at the table can see that the player's concern is genuine, and can agree on the change (and I am not limited by the rules on what we can change, after all the player could also "scrap" the PC completely and make another). Having respec rules creates limitations as well as opportunities. If you have a good social contract between players and DM, you don't need these, and they actually get in the way, because now even a good DM might be tempted to believe that there is a reason of balance behind such rules, and may not want to exceed those limitations. But retraining rules are one thing, and long-rest ability switchare another thing, obviously a lot more worrying for me, because they can happen all the time, every single long rest... this is not anymore about a safeguard against mismatching between PCs and the campaign.
I know what many players like you might be thinking: if I have to discuss with the DM then it's a "Mother may I" situation. I think this is the crux of such social contract. Way too many players are afraid of just discussing and resolving things together with other people, and they hide behind the "Mother may I", so they demand the game to be more like "yes I can because the game entitles me to". Well the bad news is that the more you rely on the game to be like that, the more your social contract at the table will sour, so you're more likely to end up with a DM who then sees you the player as an adversary, and might just house rule "no you can't". Then you (or the DM) leave the table and go back playing BG3 alone. In fact, it is not surprising at all that the general demand to RPG that they "play by themselves" always comes from people who are more interested in videogames, where there is zero social contract, and/or from people who only imagine playing the game or talk about it, but don't really have a group of people to play with around a table.
It sounds like you are saying that as a DM or as a Player, you don't like the idea of "respec" rules in the core game that empower the player. But removing those rules disempowers every other player in the world, so you can control the conversation with yours. I don't care for that level of control as a DM. I can adapt. So easily. I already do.
You as a player don't have to use respec rules if you don't want to. But if another player at the same table wants to respec to better envision their character, or adapt to new rules from a new book that better represent their vision, how does that negatively impact you? What if they worked with the DM? Does that still negatively impact you?
If the player builds around swords and the DM only gives them an awesome axe as treasure, that isn't a real choice. It's a feelbad moment. The player has to abandon their build for a cool weapon? Or get rid of the cool loot? Greeeeat options.
*Edited out an unecessary comment that wasn't productive.