Depending on how strict you are with the rules, it can be pretty a fairly quick game. It’s not super quick, but it’s no Axis and Allies or Risk.
The fact it’s a long game isn’t an issue, the problem is that it’s long and bad. A winner is usually determined pretty early on but then there’s still half an hour of random rolls as everyone slowly loses their money. That’s why house rules are mostly adding safety nets, the game’s already over and it’s just not fun running around a board watching your numbers go down. Since house rules don’t change the core gameplay they don’t fix the game and just make it drag even longer.
There’s some very good long games and some very good short games, how long a game is doesn’t determine how good it is.
I’ll have to respectfully disagree, while it’s not the best game, I can’t say it’s that bad. The whole game shouldn’t take more than 45 minutes unless you’re going easy on someone (like kids but monopoly isn’t really a friendly smiley game).
I guess it’s really up to what type of games you like to play.