You're right in principle, but it's important to remember that tradeoffs exist. You can very much trade off engineering effort and time to improve reliability.

Commercial aviation is a great example of taming extreme inherent unsafety of aircraft by applying a lot of resources to the engineering side. Another is space programs.

And car power trains have nothing on those ;) As Toyota has shown, it's totally possible to make reliable hybrid cars with enough engineering thrown at the problem.

So if all things were equal, you'd absolutely expect an EV to be more reliable than a hybrid, but all things are rarely equal.