1. Remember that Pokemon is about Ash adventuring around the world to become a Pokemon Master, it's not a romance series. Whenever romance is scarcely brought up it's also usually involves a character of the day and/or Pokemon somehow. Also remember that, despite how many real life years have gone by, in the anime world Ash is still a 10 year old boy. His only goal in life is to become a Pokemon Master and that's his main focus, moreso that over the years his character has been made to be oblivious to love that he doesn't even recognize when Pokemon mating rituals are going on.
2. Brock is very likely gone for good. He's been with Ash through 4 regions and really they weren't doing much with him. Letting Brock go allowed the writers room to now not only be able to introduce new female companions which they've been doing every region after Johto but now also introduce new male companions. This helps keep the show fresh and build upon a new character who has their own goals, skills, and quirks.