I honestly allways wondered why people even say that they would like developers to add More classes, more races, more maps, more items, more spells ... more anything.

Do you honestly think they dont know?

No, i do not think they do not know. I think some of them do not realize but cutting things like classes, spells and abilities is mostly a programming decision. Every class, spell or skill needs to fit in. D&D has a predetermied ruleset, thats one part. Changes need to be made for Video game adaption, these changes lead to unbalance and so on. In addition larian seems to like to add their own twist to things.
I guess you know that too.
Implementing the whole D&D rules that exist may be a bit much

. We can only hope :P