Many upgrades in the later chapters are far too big when you also have to place other buildings required to do a chapter.
I play every day unless I lose my internet connection, and I prefer the smaller factories to actually have an option of advancement in the game.
Take the Woodelves chapter, the Weeping Willows use 5x5 per unit and you need a lot of them to have any hope of finishing the chapter in any kind of reasonable time... often getting stuck waiting for more Mana to get anywhere.
They are gonna lose a lot of dedicated players if that demand for upgraded building production continues.
Don't close off other options, there are many ways to skin a cat and many ways to play this game.
Take for example Mana - Weeping Willows are the very basic and first major Mana building. As an introduction to Mana its perfectly fine but there are other buildings available.
Almost every event gives multiple options for Mana like the Magical Mana Hut or Manta Ray etc these are far better than basic buildings.
The Spire gives permanent buildings as a reward that are even better than event buildings too.
The Weeping Willow in Woodelves chapter gives 7.47 mana / square / hour
Magical Mana Hut in Woodelves chapter 22.92 mana / square / hour
The Spire's Mana Plant in Woodelves chapter gives 13.33 mana / square / hour without set bonus and 40 mana / square / hour with set bonus.
Another way of looking at it is that the Willow generates 4480 mana per day.
Willows requires 25 tiles to generate that.
Magical Mana Hut requires 8.15 tiles to generate that.
Mana Plant [with Set Bonus] requires 4.66 tiles to generate that.
Making the most of events and Spire is a challenge but it helps you tremendously and with RR spells you can carry your Mana Plants and Mana Huts with you.