"solves real problems and nothing bad happens most of the time."
Like Wordpress plugins previously that'll work for now but we're now on the trajectory of relearning that same lesson, because people are automating discovery and exploitation of these extensions and plugins and whatnot around text editors and MCP and so on.
Though I suspect we'll first see a torrent of exploitation similar to what was done to Wordpress instances, and then a change of behaviour, because as you allude to, the people with influence didn't learn from previous experiences with similar technologies.
I suppose people did learn that it isn't that bad or costly after all and the risk and the bandaids are still better than the cost of being the first to try and fix software supply chains for good. As things stand, I don't know how that might even be done if it's supposed to not be a better bandaid and someone has to do the legwork and it can't be so costly or impractical to overworked IT teams that everyone is just going to ignore it.