IMO Rise was a little too easy for my taste, but it brought a lot of new people to the franchise (alongside World), so I'm a little conflicted there, I did enjoy my time with Rise, though!
Also, great to see what appears to be a day-one Steam release, crazy to see Capcom learning.
MH:W was my entry into the series. It seemed to have a decent amount of monsters in it for the base game. How does that stack up to earlier titles like you were saying? That being said, there definitely could have been more, but the detail into the models and the game in general may have been a factor that they didn't include as many as you're saying.
But now, with World behind us, Capcom might see the writing on the wall that more people are playing World than Rise on Steam at any given point on the day and sink more time into adding in more base game monsters.