Re: non-Terran President of the Federation - Star Trek: Discovery in its fourth season offers the intriguing Laira Rillak, whose ancestry is Cardassian AND Bajoran. (Btw, given that we're dealing with a universe full of interacting civilisations who have been interacting for centuries, people who aren't from one world but several in their biology should be far more common.) As a major supporting character. And of course in the s3 and s4 of Disco era, Earth hasn't beeen a member of the Federation for eons and only rejoins at the end of s4, so it's the antihesis of Earth centric. One of many reasons why Discovery is my favourite of the new bunch.

As to the popular acclaim - I do think it's nostalgia, pure and simple. But to each their own. Telling someone they should not enjoy something never works. I just know I won't watch that season ever again.