Perhaps my mistake was in assuming they're oriented for the early game. I'll grant the UI is stronger when you have more tiles worked, and the UA is stronger when there are more cities with pastures and camps. Just because these become available early doesn't mean you have to focus on them early. So, help me out, what's a typical build order for a successful game with the Cree? Are you punting archers and monuments to get their UI and UU up, or just use the UI later when you have people to work it?
The free tiles still seem overrated. How often do trade routes go over the exact tile you need to hook up? As for stealing enemy city tiles, again, you're almost always invading a city that close anyway, and soon.
Yeah, when I played them I didn't actually built their UI much in the very early game (and probably built maybe 2 of their UU total). I certainly grabbed pottery earlier than I usually do for the trader.
For ancient era, I'd just make sure to build at least one UU and place one UI as that'll basically get you a classical golden age. Otherwise I wouldn't prioritize the UI above luxes/pastures etc. at the start (unless you have a city without fresh water - use it to pump the housing up quickly). It would be the next round.
When expanding, see if you can place an early city spot with good number of pasture/camps, and get those up, as a prime trade route spot.
The extra trade route tiles are definitely more a 'bonus' than a specific strategy. It's like faster expansion more than a guarantee you'd be able to grab something.