Is the custom web agency business model dying?

I feel like a lot of companies like Upwork are popping up every now and then and on the other side, developers are more inclined to work as a freelancer rather than fulltime employee. And the trend that people hire full-time employees on the bigger roles only(Directors, Leads, etc) and work with contractors.

Also, the fact that these companies do pay really well. I'm not really sure, but in the future won't it be difficult to hire talent for a web agency?

I'm actually in a phase where I need to decide which to choose from the product of my own vs the web agency(I have a few clients already).