People tend to thing EV batteries are a binary thing, they are either working or broken. This is not how it goes.
An EV battery loses capacity faster in the beginning, slower later on. The falloff is perfectly predictable and easily estimated. You can check the health of a battery pack with a free app and a $10 OBD2 reader when buying one.
Yes, the maximum range will be lower than it was new, but it's up to the buyer if that is something that bothers them.
Compare this to the process of buying an old car. There's no way to know what kind of crap oil the previous owner has put in. You can't tell what shape the engine is in without actually opening it. The gearbox might just decide to break one day, the clutch might be on its last legs and the pistons might just come up for air some sunny summer day to enjoy the weather.
The only way to check for faults is relying on educated guesses (bring a friend who knows the specific type of car or take it to a shop for evaluation).
The difference between an ICE and EV is that ICE needs money frequently (oil changes, belts and chains and whatever wear down), an EV has That One Big Repair coming up at some point. And the price of batteries is steadily going down.
For example you can get a 3rd party battery for a Nissan Leaf _today_ that's 30% larger than the one that was in it originally. Just think what we can do in 2030.