All those parts can be bought essentially off the shelf. It’s obviously not anyone can do it, but certainly the barrier to entry has been significantly lowered.
Combustion engines can be bought essentially off-the-shelf too.
Which parts do I choose? How do I assemble them? How do I make sure they all fit together? Plus as another commenter pointed out, I can buy an off-the-shelf combustion engine. So by your logic, it should be just as easy to build an ICE car. Yet neither is easy to design/build.