I use build tags for integration tests, however they’re not for enabling/disabling the tests, but for selecting different suites. It works fine, having no tags is running everything, but sometimes that’s too long so you can slice into the problem you want to test for. Tags are ideal for that.
At the same time there are cases when you just have to test different code paths, and that’s just not something you can do with environment variables.
Also patronizing the people that work on the same codebase as not knowing the tooling of the programming language is a poor reason for not using them in my opinion.