I see your point and while i agree that freedom is a good thing but i have several issues with the personal rules suggestion. Before i get to it, I want to say I like a lot of things in the game, so its not like i dont like everything Larian added to it or the overall direction they took. But as Larian said multiple times this is EA, its not about bugfixing but feedback on feel of the game and features, and there is a significant volume of people including me who likes the game but would like some feasable to implement tweaks implemented in-game for some of the rules so we can enjoy the game even more. Personally I dont care if a feature is less DND or not, im only interested in the overall feel of the game.
One issue i have with personal rule is that i don't really like to pay attention during gameplay to what personal rules i need to maintain, i prefer if the game I bought ensures that part once i set it up. i plan to play this game in coop as well, if all of us need to set and keep in mind personal rules its just even messier than the game letting us on agree on one preset of the rules beforehand.
Second, and i think most important one for me, is that its a completely different mindset you have when you are going into a battle or even plan with your resources before that, if you know you wont be really in "danger" even if you screw up you wont be in trouble probably. Another player's sacrifice matters less if we know its not really a sacrifice. The game becomes less tense, less exciting if you are the type of person who needs more challenge. This is subjective obviously, but i dont think im alone thinking that at the moment bg3 could be a little bit more tactical and it would be nice if it would have more meaningful resource management or some kind of mode which makes it more challenging. You can of course imagine for example that you HAVE TO prepare more resources before the next encounters because you will forbid yourself to long rest (which atm can make you skip some story in bg3 actually but thats another topic) or you say to yourself you cannot eat healing food during combat, but it will never feel the same, winning the battle will just never feel as rewarding as it could be when you win by the set rules with clever tactic. You just wont be trying that hard to win a hard fight, you wont feel that frightened when suddenly enemies surround you.
Third is that i think customizable rules can add to the game in long term. I plan to play the game multiple times so these could help to spice things up for additional playthroughs. Also these actually can help the devs to appeal to an even wider audience by giving more options.
Customizable rules (a lot of depth RPGs have some for a reason, Pathfinder, Pillars) can be overwhelming for new players so most clever way to do it is to have presets (this can be like "Authentical", "Homebrew" modes etc.) so people who doesnt want to deal with that just choose what they like and can get to the game quickly without starting to toggle everything. I agree its best to keep the current light setup of rules as a Story mode option or something (can be default, thats fine by me) there as a lot of players like to play like that for sure. But its clear there is a significant portion of players who like the game but would even like it more with some minor tweaks. Also people who play without these more restrictive rules would be able to try out the game with a different flavour once they got the hang of the lighter version and just see how the feeling of the game changes and becomes more challening. I can imagine the game can grow even more on them too. Thats just my 2 cents on it!
English is not my native language so sorry if im not easy to understand.