I've never been able to understand this idea that someone else owes you their time.
There's one more Province, and it will decide the game. I can see that your engine has kicked off, and you're going to win the game. Sometimes these turns can take awhile, and sometimes they don't, but exactly why should I now have to sit here and wait for it to finish? Because it would be rude? Or if we're halfway through the game, and I can tell I'm far behind, maybe I made the wrong decision, going for some stupid Alt VP strategy when clearly the HoP megaturn was the right call. I understand that it would be fun for you to play this game to its conclusion so you can actually pull off that turn. But do I now owe you the next five minutes of my life because you're better at Dominion than me? No, I'm resigning the game and moving on. I will at least say "good game" before moving on, but that's as much as you should reasonably expect. If you want to always play games that actually finish, play against bots, but if you're playing online get used to people moving on to the next game.
On a different note, I don't think it's an issue with point counters. Maybe it would be nice if you could finish the game against a Bot. Something to possibly look forward to in Dominion 2017.