Power Factor Correction Controller IC limits
A controller like the UCC28180 (or generally, any switching power supply controller) is limited by the external components that it can practically drive. The extent of "practical" depends on the design requirements, e.g. efficiency, cost, size, which have a distinct relationship with the non-controller component selection. 

The UCC28180 datasheet states that it has an "integrated 1.5-A and 2-A (SRC-SNK) peak gate drive output". In applications such as the TIDA-010081 1 kW reference design, this is circumvented (pg. 2) by utilizing an additional driver IC, an UCC27517 to drive the IPW60R060C7 600 V boost FET. The PMP8740 2 kW charger reference design goes even further, using two parallel UCC27517 driving IPP65R125C7 650 V FETs from the UCC28180 output. By comparison, the smaller reference designs like the TIDA-01494 480 W supply, the UCC28180 is used to directly drive the TK31N60X 600 V FET.

Another practical limitation is that this controller is only suitable for operating with single-phase input power. In the US, this would typically be 120 V at 15 A, usually leading to ~1200 W output supplies maximum. A full 2 kW of power supply, like in an ATX supply requires 230/240 V AC input to operate on a single phase. Even higher power would be served by a 20 or 50 A circuit or by expanding to three phase power, which would require a different front-end PFC implementation.

To summarize, you cannot ignore the other components of the PFC implementation, the environment your implementation will be used in matters, and quantum mechanics need not be a thought in the engineer's mind when designing in a PFC controller.