Well, as I understand, many players already started specializing their settlements based on adjacency bonuses and it's a new layer of fun. I myself, just starting that sort of planning, but I wasn't great at city specialization in Civ5 and Civ6 either.
The idea is generally the same, adjacency bonuses define spots for particular buildings, plus Civ7 allows to intensify this with resources. Specialization with resource allocation is new and really powerful.
So, I'd say city specialization is already quite good, just hard to master.