I think for certain technology and privacy focused individuals, Mastodon and Lemmy are the way forward. Some people will always prefer a centralized solution or just don't care enough to make the switch. They will continue to be the userbase of websites like Digg, Reddit, and Twitter.
And to be honest, I don't see that as a bad thing. I find the content here is actually worth reading through almost every comment, whereas on Reddit/Digg/Twitter I'd scroll past hundreds at a time because of how low-quality they looked.
Yeah I think a bit of a barrier to entry is actually a good thing, in a way. Keeps low quality content to a minimum and the discussions more authentic. At least this is what reddit (or even the Internet, in general) was back in the day.
Yes the easiness of registering to reddit have also contributed to it's dumbing down. People who just follows the trend basically overwhelmed the culture of that site. And i hope the perceived difficulty in using Lemmy acts as an effective barrier to those kind of demographic.