> The high parasitic capacitance of solderless breadboard makes it unusable above about 10MHz. You also have to deal with unpredictable contact resistance.
Most of which really isn't a problem with digital circuitry and microcontrollers because most of the peripherals are on board and your communication buses are all low speed (most <1MHz--USB being the exception).
The biggest issue with modern circuits is that even your low-speed clock lines need to have series termination resistors--even at low speed--even on a PCB. This is a weird artifact for an amateur to grasp.
The issue is that even the cheapest digital chips nowadays have super high-performance transistors on their I/O. Consequently, a 10 cent microcontroller can respond to a 1GHz signal bounce or reflection on a 100KHz clock line. And, oddly, an FR-4 board makes this worse, not better than a solderless breadboard.
Electronics hobbyists would be well-advised to learn SPICE as quickly as possible - breadboards are an endless source of frustration once you move beyond the basics.