Starting at level 1 works well for BG1, and Dragon Age 1 because you and your first companions are fresh adventurers. I am unsure it works with BG3 because all the companions, including the player character, have detailed stories going back years.
I think a good solution would be to add an option to allow players to start at 3rd level, and level shifting the whole game as a result. That way you aren't a squishy first level fresh adventurer but instead just not a powerful one. If would also allow players to try different builds rapidly instead of playing for several hours to try new subclasses should they have to reach 3rd level to make those decisions.
This also gives the bosses access to more abilities and spells which could make those fights more interesting.
I only think that this should be an option though as starting at 1st level is an easy way to start the game.
