I am going to respond based on the experience I had with epic buildings in the cities I deleted earlier this year (and the deleting was indirectly caused by the amount of epic buildings I had)
- I did epic projects almost weekly at one point, but slowed down over time as my city became "mature" and the amount of skyscrapers I had for epic projects dwindled.
- There is absolutely nothing fun about building an epic project - if you enjoy producing items and navigating the global market for what you need to complete a task for the epic project - you must have a lot more freetime than I do. I usually loved the end product, with the exception of the educational epic buildings, those are ugly imo. The reason I completed epic projects was for the token parts, and to give my city a visual upgrade. The residential skyscraper buildings are incredibly generic and sometimes very repetitive which for me being a style snob at the time, I had specific style palettes for each region (only specific residence types like sunny or frosty in the applicable regions with specific specialty epics being bult). It was serious business for me.
- The big reason I deleted my cities really had a lot to do with epics (I'm on topic bear with me) was the amount of service consumption they required with the services 2.0 upgrade. I was already very unhappy with the clear lack of empathy those in power had for the players who had to tear up years old designs, but the amount of services that was going to be required to making my city functioning would have required a lot of time and resource investment. Another thing I didn't like is the wide variety of materials / supplies / items needed to satisfy the tasks for the epic project - I already had five regions unlocked when the "new" (aka mostly recycled) shops were added to the game like the sports shop, etc. It just made epic projects even more challenging. I think the best way to make epic projects "funner" would be to redesign the whole thing, lighten the requirements somehow in terms of points needed, variety of materials / supplies needed, or something similar. Also, give players an option to request the task be refreshed with different items (like the same way we can do for upgrading buildings, it's another opportunity to make people watch videos!). If you're afraid of everyone overdoing it with refreshing, limit video watching opportunity and make the wait time like an hour. And lastly (and most unlikely), reduce the service requirements for Epic buildings (and Omegas).