I think ebikes are great, especially for commuting/transportation. I've ridden them on road and offroad (including up AF canyon, where they're legal), and in my mind it's the worst of both a moto and a mtb. They are kinda ok on the up (but a moto is way more fun up), but they suck on the down (a MTB is way more fun on the down). I'd much rather ride a moto or a regular mountain bike than an ebike in the mountains. The pedal assist definitely helps on the ups, but the bike is a tank and doesn't handle like a regular MTB.
My issue with them is the potential land access issues. It's not because I think they cause more erosion, it's because the lobbyists will think they cause more erosion, or higher speeds, or they see the motor. And then they won't be able to distinguish between ebikes and regular bikes, and it'll be easier to just ban them all. Maybe I'm cynical from growing up in the birthplace of mountain biking (the bay area) where you get a $500 ticket for going over 15 mph on your bike. Or where 90% of my favorite trails as a kid are now illegal for mountain bikes. And that was before ebikes were on the radar.
One other issue I'm seeing is how easy it is to hack them. There are a bunch of YouTube videos on how to remove the governor, or add a thumb throttle. I was at sea otter and a vendor came up to me showing me his new DH ebike. 3" plus tires, dual crown forks, full suspension, and he flipped a switch and said it'd go 50 mph with no pedalling. I said "sounds like a moto" and he said EXACTLY, only now I can ride on MTB trails." Then he demonstrated the thumb throttle. It was an e motorcycle. And don't get me wrong, I think emotos are cool too, but when MTB trails are already walking a fine line with access issues in some areas of the country, adding a motor only complicates the issue.
If I had a crystal ball that could show that ebikes would never lead to any singletrack trails getting shut down for traditional MTBers, I'd be 100% in favor of them. I have no issues with someone using pedal assist. I'm not ever going to buy one, but I don't care if others do.
Personally, I love a simple bicycle. I love the feeling of pedaling my bike up a mountain, and then pointing back down and letting gravity do the work.