Even with feedback from the community, it's, what, 1% of the population that regularly plays Dominion? That wouldn't have changed the decision because hardly anyone would have voted in favor of keeping it. Most people don't care.
And you talk about Smite when they did the same thing. Joust isn't comparable to Dominion. Domination was Smite's Dominion and they deleted it for the same reasons Riot did. Now, I was one of the players who regularly played Domination, and it was my favorite mode by far, and I and players like me were upset and made posts... To this day, you'll occasionally see a post about how they should bring it back (usually in the form of a YouTube #remember sort of comment). But the vast majority of Smite players don't care at all, and even the majority of those who used to care have gotten well over it.
You'll get over it, too. It sucks, but it's not the end of the world. You said you were a father, so act like an adult and stop whining and calling things "stupid" and threatening to leave over a decision you don't like. Give an actual argument for it. It's really not a mode that was worth keeping active, even if something like 10% of the population played it. That's just the long and sort of it. Sorry. :|