Those concerns are valid - within the context of organized play like AL.
Within that context (and there is an AL forum here), it makes a lot of sense to voice them, and to have a reasonable expectation that AL not adopt overly 'controversial' new options, or at least leave to individually DMs the option of allowing them or not.
I think it's valid beyond AL. DMs are a finite resource. You may not be able to simply "find a new DM".
Or maybe you've been playing with the same group for years, and you like everything about your table and the DM
except that he (she) has a penchant for allowing anything that's "official".
Or maybe you *are* the DM and you like to be inclusive, but you know there are a handful of people who show up wingeing and demanding that you allow "official" content, and the ensuing arguments spoil the atmosphere.
Yes, there are solutions to all of these things. But:
1) They are all examples of how the impact of undesirable content (whether it's complexity or specific classes you detest) is more complex than "if you don't like it don't use it".
2) There's also a solution to not having the complexity: use unofficial content.
Again, not trying to argue that one side or the other is right, just that opposition to new forms of content isn't by definition selfish. (Nor is discussing that opposition in this forum, even if one's opposition is solely based on AL.)