I disagree. The cost of onboarding a new developer is negligible compared to the cost of picking the wrong stack for a project just because it might be the hipp

I disagree. The cost of onboarding a new developer is negligible compared to the cost of picking the wrong stack for a project just because it might be the hippest tool at the time. An experienced programmer can pick up a new framework in a week or two tops and their ability to pick up the application code will have more to do with the quality and documentation of said code than anything else, but if you pick the wrong framework you'll be paying for it for the life of the project (or until you refactor with a new framework and write a blog post about why you decided to switch). If the tools you're using cause your code to be inherently difficult to grok, then that is an engineering problem, but that has nothing to do with how fashionable the tool might be.