I'm puzzled by this read on the situation. For starters, vanishingly few programmers work in a pure functional context. Secondly, performance characteristics of functional programming are absolutely not dogshit. There are specific languages/VMs/etc that have inherent performance issues, but that's not a universal truth. To claim that would be like pointing at Ruby and saying that imperative programming is slow.
I think maybe a more measured take is that many modern environments remove the developer sufficiently from the actual execution of their code that performance optimization becomes much less obvious and straightforward.
Also, and this is just my personal experience, but I've basically never heard anyone actually claim that optimization is bad or unnecessary. I have never, ever heard anyone claim that profiling tools are bad.
What I have repeatedly heard is that there often isn't a compelling business case for performance optimization. Unfortunately that's probably correct a lot of the time.
I really think you're pointing at the wrong folks here. The hordes of JS devs out there who are deprioritizing perf aren't doing so because they think it's fundamentally a bad thing to optimize, that's just a self-apparently ridiculous notion, they are doing so because they work in a culture that values delivery of features massively more than optimization.
JS developers have largely accepted the FP way of life, it’s why many JS apps are as slow as they are despite JS being actually quite fast.
I don’t think that has anything to do with FP honestly. I think it’s a combination of package culture, the language making it incredibly easy to write poorly performing code, and the massive scale and cultural/corporate tilt of the JS community resulting in a generally lower quality of developer.