This argument is only being made because widespread EV adoption is a new phenomenon and they are still a fraction of the market of ICE cars.
We could flip the tables around. Modern car engines are highly precise machines. If we were just starting to make them, they too would have enormous supply chain problems. Only a couple of companies would realistically be able to produce the components with the required tolerances and lifespan.
Once most cars on the road are EVs, we'll have plenty of suppliers.
And yes, EVs _are_ reliable. Orders of magnitude less components and even fewer moving parts. ICE vehicles require a whole chain supplying more stuff all the time, even for vehicles already on the road.
Oh, and don't get started on battery materials. We too thought that our oil reserves were not able to satisfy the demand of so many cars (not to mention other industries). We found new reserves and some that were not economically feasible became available, as technology (and demand) improved.