There are some quite different PICs. Some are ARM.
The 16 and 18 Series are the alternative to 8051 and AVR/Ardunio They are best programmed using JAL V2.
NXP do M0 ARM chips about same price as PIC and AVR. But some projects are so simple that a PIC or AVR is cheaper to develop and maintain.
The huge advantage is that switching PICs and setting the device options are easy. The team also have figured out most of the mistakes in datasheets. There is even a PCB that takes Ardunio shields (which are physically a daft idea!).
JAL libraries are good too, USB, FAT, SD Cards, Graphic and Text panels, Maths etc. You can swap between bit banged GPIO or dedicated I2C, Serial etc HW with JAL libraries.
An Ardunio is for people that can't solder veroboard or order cheap custom PCB from China. AVR and PIC are equally easy to use without that ecosystem.