If you always have a smooth-talking bard because the game doesn't make you narrow your party down, you might never learn about those other options.
If you always have a full skillset available, there is a tendency to fall into the habit of doing whatever seems the most obvious, which is probably the same thing over and over again and tends not to be as fun.
ya i still dont agree with your logic or rationale here fam but enjoyed the life sharing
1) as a player, you dont need to choose to use the smooth-talking bard for every encounter - you can use the strengths of your other companions for any of the variety of scenarios you detailed above. in fact, if im restricted to four party members then i for sure will not learn about those other options or varied strategies bc the game is arbitrarily limiting my adventure party to four ppl already. (disregarding multiple playthrus - which is a different discussion)
2) respectfully, not really sure how to even respond to the second comment particularly given the current development status of bg3's ea build. idk, id say that if we had the full skillset, which can be interpreted as having the traditional 6person BG party size, or more class/race options, or a closer adherence to 5e balancing then maybe larian's ea build would be more fun? there at least would be less need for the larian cheese/exploits currently in ea and swen may actually show content during his panel playthroughs that dont consist of 'gaming' boss encounters
if you like the restrictions that a four person party currently imposes, have at it, you can still run with just four if the party size gets bumped to six, but atleast the rest of us wouldnt need to be subject to the same 'interesting' restrictions
2) if they just bump it up to 6, they will adjust the difficulty of combat to match, so it would be silly to then run 4. Also, everything I have read about 5e it is targeted at 3-5 party, not 6. Six was 2e and 3e.