Batteries can be replaced. An EV that could run 1 million miles would still need maintenance - I think the point is that they could be designed to last.
Planned obsolescence is so wide spread we don't even notice it, but lots of products are designed to fail either through cheaper components or deliberately flawed design. That means we have to go and buy a replacement. It is also generally cheaper.
So we either have cheap products that will break or seemingly expensive products but they last for a very long time. But in the long run the cheap products generally cost you more to buy than one expensive product.
I don't think the wider population would accept the compromises necessary for a million miles vehicle. There is always a balance between component longevity, cost, performance, features, and safety.
They can exist but I don't forsee wide adoption due to it being wildly expensive and/or bare bones in terms of contemporary features.
I think the big part with cars is people want the new shiny thing.
The only people I've ever met who didn't trade in a for shiny and new were my fellow cheap bastardin' mechanin' types who just don't care.
Plus, too many people think cars must be serviced at "stealerships", and I've seen what those lying bastards tell people their cars need. Like a 2 year old Toyota with 25,000 miles needing $4000 of engine leak repairs. On an engine that Toyota has manufactured since the 80's...they don't leak, they don't even die. Hell, they still use a timing chain rather than a belt, so that's maintenance it'll never need.
Csrs don't need replacing anywhere near as often as most people replace them. As I said elsewhere - my current daily driver is 18 years old, everything still works. It's required very little regular maintenance over its life. Transmission was replaced at 200,000 only because a cooling line leaked into the transmission, which destroys the clutches eventually (it went 50,000 miles after the line failure, even towed stuff at max load).
Batteries will be very expensive, however. The battery company is still quite greedy, eyeing for 5~10x growth in the near future - and that requires raising battery prices by at least twice.
Yes, the batteries would need to be replaced but that means designing them to be replaced.
Unlike the Tesla model Y which built the battery into the frame and filled it with foam so that it absolutely cannot get replaced. Musk said the way to replace the battery is to send the entire car to the scrap yard and recover the lithium from the shredder.
My 2013 Model S has 235,000 miles on it and still l
drives like it's brand new. I haven't yet had to replace the battery pack but when that day comes, it will almost certainly be worth the cost.
Here is the link where Sandy Munroe determined the Model Y pack is non repairable and it includes Elon Musk's reply tweet saying the pack should be seen as "high grade ore".