Yea sorry, it’s a tricky question in fact and in another way, it’s easy to make a joke on this kind of speech. Moreover, I do not have 15+ years of experience, so they know a lot more than me obviously.
However it ticks me because at my last job, the next guideline was to use Go for new back-end developments, even if only few back-end developers had experience with the language. I didn’t see it as a game changer for us in despite of the internal speech.
Firstly, Go seems to be a good language. I don’t like it for the few I read and tried, but who cares? It can produced statically type checked executable with a build-in garbage collector (e.g. some techs see it as a good fit for AWS Lambda). It’s seems to be in my sense in-the-middle between Rust and Elixir: not safe as Rust but easier to master with similar efficiency (let’s say less than 2 times slower), and without the resilience (and the accidental pseudo infinite scalability) of Elixir but way faster per process and built-in concurrency patterns. But if you are looking for a the “chosen one language” because messing with many tools is a pain, it’s a choice to consider.
Secondly, I understand the “cult” you can have on a tool or tool set. I feel the same with Elixir, even if I do not consider myself advanced on this topic. I’m remembering right now moments where people look at me before I talk saying as a joke: “Elixir of course?”. In fact, I try to not answer this myself because I feel a lot of “I really want to use Elixir so I suppose I can’t be impartial to choose the right tool for the right job”.
It’s sometimes hard but we have to, as “software engineer”, to do our best to be pragmatic. A tech lead have to consider multiple parameters: the domain, the tech communities, the tool sets associated with languages, the internal team knowledge… Development speed and production costs can be estimated from this points. But we can add to the list your team wishes/believes is to take into account because it’s not false to say it’s a way to innovate and have fun at work (but not the only way of course). To put on the top the last one as main argument is a mistake.
A recommendation could be to come back to challenge them about their speech, e.g. what is your current and next hosting strategy, which languages did you consider before making this choice, and so why Go, what kind of problem does it solved for you, why a no framework strategy (I really do not understand the last one BTW) 
.
).
