I didn't really enjoy the first season of 86 and I don't plan to watch the second, but I guess there is people who likes it.
To me, it is just a subpar cgi-infested mecha with some forced tragedy points.
The cliches are annoying and I don't particularly feel anything for the other characters which might as well die on ep 1 and you wouldn't notice. This despite they trying really hard to sell their deaths as a tragic loss. They are not.
The plot brings some interesting ideas which are welcome but you can see their 'twists' two football fields away, I found myself most of the time thinking of how could have things played out had they made something different.
As for who likes it or why is it popular, IMO that's mostly on the chans simping the core plot for reasons I cannot express in these forums.
But hey, I want to see what Diano sees on it too