Blizzard do put out quality games.
But one of the main reasons is because the games that they make are huge money makers..... I would seriously doubt that they even consider making a game that is for a niche market. And pump as much money into a game that is not going to sell millions of copies.
Quality game cost lots of money to make and the return on a sub sim wouldn't be worth pumping huge amount of money into.
Hench why SH5 is unfinished. Ubi didn't see this game selling millions of copies, so wouldn't extend the due date to when it would be ready. As doing so would mean less profit (
IF they even made a profit from it).