I work in software development too, and I can tell you you're full of it. Every whiner in here is insufferable. But to get to the point:
The game does not have "major bugs". Major bugs are ones where the game crashes or doesn't start or has UI elements that don't work. Major bugs were when CM4 showed up and the game result would change after half-time. These things don't happen with FM. Defenders occasionally making a mistake or a bit more often than usual is not a "major bug". As a software developer, you should know this.
Software estimates are hard - something you yourself point out. There are too many unknown unknowns, though SI does have the luxury of knowing their domain entirely and working essentially on one product for a few platforms. They're not that much affected by external forces, like some other IT companies are. And of course they use their previous experience, why the hell do you think they don't?
The game is definitely "playable". Unless you got zero hours out of it since you bought it, you have played your heart out of it. With football in general, everyone will have their own idea on what it's "supposed" to look like, even more so with simulated football, so you will never be entirely happy with any football simulation until you learn to relax and have fun, and give a pat on the back to your fellow developers that try to simulate a game that, in real life, has rules open to interpretations and opinions. It's an impossible task they've taken on themselves and their end result is phenomenal and yet, here you are, taking a dump on it. As a client, you're, again, insufferable.