There are a couple of points we need to remember about brand new content as opposed to regular predictable content. New ideas take longer to make and require more resources and balancing. They are also much riskier, as they have not yet been proven successful. They are usually worth it, but the developers cannot reinvent the game with every patch.

One of the reasons we get patches so regularly is because the developers have a template to start from. It makes this game a reliable source of entertainment because I always know I'm going to get more of the content that I enjoy. With that said though, I also like when they try new things, as they have been with LoV, the Diadem, Aquapolis, and PotD. Some of them are successful and some are not, but that's the risk you take with new ideas. Personally, I think we get a good balance.

As for the complaint that there is not enough content to last for 3 months, content will always be consumed faster than it can be made. This is true for most entertainment, whether it be books, movies, video games, etc. In 3.4 we are getting main story quests, 2 dungeons, Alex the Creator, an ex primal, housing, Hildibrand, the scholasticate, dueling, Squadrons, PotD (in 3.45), new crafting recipies, as well as QoL changes. I think that is a lot, personally. Iirc, Yoshi P has said that he is happy with the content he has created so far, but he wants to put out even more. I believe the developers are doing as much as they can atm. Hopefully they can find more people to add to their team soon.