There's definitely enough transistors in there for a microcontroller. It only takes a few thousand. If you're building a custom integrated circuit in the first place, the cost of a microcontroller core is relatively low, and often the cheapest option. The alternative is to write the logic in a hardware description language (HDL) like Verilog, and implement it with logic gates.

The microcontroller approach uses a fixed number of transistors, with cheap mask ROM scaling with complexity, whereas the HDL approach scales its transistor usage with complexity. The HDL approach usually runs much, much faster, is far less error prone, and takes longer to develop.

Which approach is better depends a lot on the application.