This does bring up some interesting points though.
For example, Starfleet is called upon to protect the entire Federation from the Dominion. As stated above, their primary mission was supposed to be exploration, and it is the Andorians who had a large Military background and would’ve been a more logical choice to fight in the war.
Are we going to fall back to position that over the Centuries, humans and Starfleet ships became technologically superior to all other members? If that’s true, then I’d think you’d see more of those species serving in Starfleet. Wouldn’t it be more logical to assume that the other members continued to develop technology, and by the time of the Dominion War (because its the example I choose) it would be still the andorians who were the military power in the federation and they would be the ones called upon to lead the fight.
Obviously, Star Trek is a show made by humans for humans to watch, so humans would be featured.
the Federation is portrayed as being this large entity with a variety of species and cultures none of whom really feel inclined to explore space anymore. They just seem to leave it up to the humans to do their exploration and defend them now.