This is just your selection bias. Postgame for most people is - or rather was - hunting for the legendaries, filling out their national dex, doing the sidegames, rematches and generally exploring the region, because Pokemon is a fundamentally singleplayer experience. I didn't know anyone as a kid who would talk about how fun competitive battles and the Battle Tower were, I did know people who would swap action replay codes they found on different parts of the internet while talking about this cool thing they found in some corner of Sinnoh, and the most common complaint me and my friends had about B/W was its incredibly boring postgame - a complaint so common that we got BW2.
That might be true, but tell me, what's the "postgame" of the original Sun and Moon? Pretty much nothing, there is a short episode that introduces you to catching UBs(something that you can just do whenever in Ultra postgame btw, infinitely), so all you can do is play in the Battle Tree or online unless you want to put the game down and never touch it again. XY, same story, it's only Ultras and ORAS that had a better postgame and the later releases never get as many sales as the initial ones within the generation. Many players did get their start in competitive from battling in competitive facilities or online simply because there was nothing else to do, which is my point: Single player is nothing more than a drawn out tutorial for the real part of the game. It's been that way for quite a while, ever since internet became accessible enough to look up strats, look for other people to play with.
There is layers to this franchise, which determines what kind of player you are: The very outer layer are the normalfags and little kids I talked about, which never even reach Victory Road. Then you have the next layer, which is people who engage with the single player portion but never really play in the competitive facilities or bother playing online too much. The next layer, much deeper one, are the professional autists, not quite on the competitive side but those who take the game mechanics to the extreme: Breeders, Shiny Hunters, players who engage in Competitions, collect Ribbons or try to complete the National Dex, ect.
Then, you have the deepest layer which is people who not only engage in competitive side of things but are actually good at it. It takes years to get here, pretty much nothing in the single player tutorial prepares you for either Battle Tower, Battle Frontier or online competitions so you will get your teeth kicked in for quite a while, guaranteed. Not everybody is made for that, there is gamers out there who can't take losing and quit any game that won't let them win without improving. That's just the nature of the beast, but it shows you how big the separation is between each layer of the fanbase. Everybody I just described had fun in some capacity, but in their own way. You're describing one type of player, one of the outer layers, and I described the very core, funnily enough when Pokemon was popular on the DS and 3DS I was surrounded by both types. In that sense, neither of us is wrong, the postgame means something else for everyone(except for the very outer layer, which never gets there).
Notice that his voice changed from 'relaxing friend' to 'you feel that something is off'. He outright says that he is putting on a womanface voice, especially since he started pretending to be a girl since years ago. This just has me watch his latest videos on mute while putting on subtitles. (I wonder if you can train an AI on his real voice then redub his womanface videos. I waited until I archived his entire channel before I posted this.)
Poketubers are the most pathetic thing I have ever seen. Every single one is either a tranny/close to trooning out or complete bottom of the barrel grifters. FSG and BKC are the only ones tolerable enough these days.