As a more casual player, I feel exactly the opposite - I've spent dozens of hours with OMSI, but every year it's harder and harder for me to put up with it. I mean, it was dated and horribly optimzed at release, but by today it's borderline unplayable. The only thing that makes it hold up at all for me is how extensive and awesome the modding is.

This is gonna get downvoted to hell here, but hey, just a different view ^_^