DoA4 sold 0.47m. Less than 1 million.
DoA5 vanilla sold over a million. Add in ultimate and LR and its close to 2 million and that is not counting digital sales as those cant be tracked. Add in the 11 million downloads for the free version, its safe to say digital sales could have easily pushed it past 3 million sales. For a fighting game, those are respectable sales numbers.
How busy this forum are doesn't matter. A good chunk of the top players that attend tournaments are not very active on any forum. What matters is that DoA5 tournaments are still pulling 50-100 people. DoA4 tournaments again were lucky to get 10. Getting 20 participants was a good day. That is more than enough to show how the competitive community felt about DoA4.
Again, I'm glad you liked DoA4. I liked DoA4 on a casual level, but again, I have to emphasize this. COMPETITIVELY the game was shallow, this is a fact, it simply was not a good competitive fighter, it had zero depth to it, every character played exactly the same using the exact same tactics, it had no mechanics to them, nothing that made anyone unique.
DoA5 at its very basic level still plays like DoA4 though, so I'm not sure why casuals like you have an issue with it.
Edit:
Lets put it this way. The fact that I was a better player in DoA4 than in 5 speaks volumes to the simplicity that was doa4. Granted some of it could be that I'm just getting old and cant react as well anymore, but in DoA4 I could make mistake after mistake after mistake after mistake and still find a way to win. I didn't get punished for fucking something up.
In doa5 if I fuck something up I'm paying for it, and that is 100% how it should be. I made a mistake, I fucked up, the opponent is rewarded for capitalizing on that and punishing my mistake. That is how it should work. A good competitive fighting game doesn't allow you to just keep fucking up over and over and still some how win. If you can, that means you got a fighter with no mechanics in it, i.e. DoA4.