Seriously, a YouTube video is supposed to be proof that batteries last ages? What is ages? If you provide something I can read you might have been able to change my mind.
Truth is not many want to risk buying a used electric car and the depreciation reflects that.
Generally, 10-20 years and 100K-200K miles. The US requires a warranty of 8 years and 100K miles.
For newer cars it's hard to tell for sure since the tech has improved significantly in recent years. But even the earlier cars have done better than people expected.
A quick google turns up lots of sources you can read. Here are a few:
Truth is not many want to risk buying a used electric car and the depreciation reflects that.