In real life, you transition from single engine to instrument rating and then multi engine, and then you go to jet rating of your choice - my friend got a scholarship to learn with C172, and then got into the airline to earn his CPL and finally ATPL plus the type rating. He now flies the 737NGs.
Like many others have said… in MSFS, you can just jump right away to big jets, no problem. Just don’t do weird difficult approaches like A320NEO into Paro (VQPR) or 747 into Hong Kong Kai Tak. Keep it simple, just fly regular normal routes where the lands are flat, e.g., SFO-LAX or LHR-FRA for instance.
Regional turboprops or jets like ATRs or E-jets for me are more like a choice, not a necessary “transition”. They don’t offer any transitory gap lesson to “bridge” you into flying full size passenger jets like A320 or A330. Sure, the turboprops might be slower, but it is still a jet engine spinning a set of propeller blades. While you forego piston engine’s fuel-air mixture/choke control, you still have to deal with pitch, rotation, etc etc etc - you also have the prop brake and all sorts of modes. That is an additional complexity over the simple jet engine that simply blast hot jet air to propel the craft.
We currently have BAe-146 from JustFlight and CRJ from Aerosoft, they are just as fast as the big jets and as complicated. The CRJ for example, it could be said that they are a bit more complicated than the A380, since it has no autothrust. One of the few things simpler there is the auto-spoiler that you don’t have to setup.