MCU is soft programming, programmable logic chip PLD is hard programming.
The circuit in the MCU is fixed, and it is programmed to do only the inherent dozens of instructions. And it's done one by one.
The circuit in PLD is not determined, its programming is the programming of the circuit, that is, the design of the circuit module. The modules are parallel.
Resources in the MCU are fixed, for example, a certain model has only one timer and one IO interrupt. The program just controls that.
PLD circuit is not determined, want to make several timers, or interrupt, or PWM output, or other modules. It's up to the program.
The MCU is like a train that can only run on well-built tracks.
PLD means planes can fly wherever they want. Or like 72 changed Sun Wukong, can become a train to run, can also become a plane to fly.
PLD VHDL or Verilog language programming.