mudguard:
I would say this because it's attracting a demographic that can afford them. IE with minimal stereotyping, an e-bike (mountain bike) allows someone who previously was not able to participate to get out on trails. Now whether this is a good or a bad thing is still a furious debate.
You're average 16 year old isn't buying these.
I still think there are some things to keep an eye out. Drivetrain spec no longer matters, an e-bike will wear through high end stuff like no one's business. Manufacturers are aware of this and slowly changing, but you simply don't need the same range or light weight.
Motors and batteries. These are the bulk of the cost, and bike companies being bike companies, there is no guarantee of replacement if something goes wrong in 3-4 years. Then you're left with a very heavy push bike.
I was up at Woodhill last weekend and was shocked at how many younger riders were on eBikes. Whole families were on them, which completely blew me away.
But you're right - there are a lot of eBikers that are not terribly capable on a mountain bike and are up in parts of the forest they really shouldn't be, without the skillset or trail etiquette to deal with all that comes with it. But I try not to gatekeep, as it's a sport I love and want as many people involved in it as possible. I just want them all to use their noggins once in a while.
Re drivetrains - the vast majority of eBike manufacturers are now speccing Deore/SLX or NX/GX with cheaper Steel cassettes on their mid range bikes. XT and X01 etc are being reserved for the higher end, with good reason. I am actually OK with that as the steel cassettes are more durable and the few grams of extra weight mean nothing on a 25kg bike.
Motor-wise, I noticed that the Shimano motors are now available as an after-market purchase (assumedly to cover those that are out of warranty) and they start at about $1500 a piece. Then you add the other parts like controllers, batteries and BMS etc...madness. But I'd wager that a lot of bike manufacturers offer longer warranties as they have the power to hassle the suppliers into honouring their obligations beyond a couple of years (Merida for example, offer a lifetime warranty - which is expected to be 10 years).