I went to school for mechanical engineering (though I now work in software). We were required to take signals and systems, but if I remember right it was a weed-out course for most MechEs (it certainly was a challenge for me, though I think that had more to do with the curriculum than the topic).
Those lessons might have been hard-won on my part, but I definitely still use them. The general concepts (feedback loops etc) are applicable basically everywhere in life, and I still find uses for literal actual math (like using a convolution kernel to do rolling window sampling in numpy).
That's not considered signals and systems, at least not where I went to school (unless you're talking about fully-active suspensions, but those are very rare and highly specialized). Rather, that would be down the "dynamics" course progression -- which is bread and butter for MechEs in those lines of work. That's also extremely useful, but it's generally a different subject matter, at least until you get into graduate-level dynamics combined with upper-undergrad-to-graduate-level numerical methods.
Vibration isolation can definitely be thought of within a systems framework, although it's perhaps overkill for passive filtering as you won't be doing much in the way of feedback.
Those lessons might have been hard-won on my part, but I definitely still use them. The general concepts (feedback loops etc) are applicable basically everywhere in life, and I still find uses for literal actual math (like using a convolution kernel to do rolling window sampling in numpy).