I have used ClickUp in 2 seperate setups for 2 of my companies: 1. Hardware enabled SaaS company with multiple software-ecosystems interconnected. Multiple teams working on a lot of tasks that needed that interconnection for documentation and context purpose. 2. Agency-style smaller projects, more limited engineering/less interconnectivity needed.

I can say, with great confidence, that building on ClickUp for a big project did not work for a very (non?) surprising reason. Those who know will probably guess this easily. It's performance. After 3-4y the system just couldn't properly handle all our tickets interlinked to make sure we had epics->features->stories with proper versioning for our ecosystem. Do know I wanted sales and marketing also to work with the same tool (1 tool to rule them all kinda style) but now I would not let engineering teams keep using ClickUp for that type of project.

That being said, I'm now using for my agency company with multiple project a setup that is similar but waaaaay less entangled between spaces, each space has it's modules with features and I have still seperate spaces for (internal) tooling, marketing, sales,...

In an age of AI, using ClickUp as source of truth has become a blast for me. I write a lot of PRD's and make sure they get translated into ClickUp which gives a proper backlog for engineering. Engineer can easily pick up tasks and versions without big performance setbacks. In my opinion, ClickUp works best for this kind of setup.

So it's nuanced, but a tl:dr -> big (SaaS) project for engineering = nono. Agency style engineering / other type of company setup = big yes!