I wouldn't call it harmless. The feature might just be brevity enhancement for CRTP (and I think it's incredibly well-designed for that), but the advertisement/education around it usually just mentions constness-agnosticism and code deduplication as the use cases, which are precisely the wrong cases for deducing this. CRTP was never the solution for those and that hasn't changed with the syntax -- because both of these have effects on code semantics, not just syntax. But I will bet most people using it will use it for those purposes, rather than as a briefer syntax for when they would've otherwise used CRTP.
It feels a lot like the push_back -> emplace_back thing, where the feature has important use cases, but plenty of people will use it merely because they're mistaught that it's the "modern way" to do things without being told it's a footgun that bypasses existing safety features in the language, and it becomes impossible to hold back the flood. And they get away with it the majority of the time, but every now and then they end up introducing subtle bugs that are painful to debug.
But hey it's the shiny modern hammer, so obviously you can't just let it sit there. People can't just see a modern hammer and let you watch it sit there until you actually need it. You have to use it (and people will tell you to use it during code reviews) or everyone will look down on you for being so old-fashioned and anti-"progress".
It feels a lot like the push_back -> emplace_back thing, where the feature has important use cases, but plenty of people will use it merely because they're mistaught that it's the "modern way" to do things without being told it's a footgun that bypasses existing safety features in the language, and it becomes impossible to hold back the flood. And they get away with it the majority of the time, but every now and then they end up introducing subtle bugs that are painful to debug.
But hey it's the shiny modern hammer, so obviously you can't just let it sit there. People can't just see a modern hammer and let you watch it sit there until you actually need it. You have to use it (and people will tell you to use it during code reviews) or everyone will look down on you for being so old-fashioned and anti-"progress".