Same impression here - I think my last 'exciting' OS X update was back at Snow Leopard when they made a concerted effort on performance (anyone ever benchmarking the now-old Mac servers on OS X vs same HW on Linux would understand how 'not stellar' OS X thread performance is/was). It's possible I've missed some 'rely on daily' OS X feature that was introduced since then, but can't think of one. The reduced horizontal scroll bars on restyle - meh.
The SSD improvements are certainly notable, so much so I 'missed' them until picking up a newer MBP for my wife and benchmarking it. Retina was notable, although I'd run it in non-retina to get usable resolution (e.g. my current MBP has 1680x1080 matte screen - I'd run 1920x1200 on a retina 15"). TB was useful overall, and TB3 (sigh, with dongles) will ultimately be a step forward, if we finally see wider-spread adoption before the next hardware bump (e.g. how many are doing chained displays + USB3+ hubs currently? Seems like not so many...and I just bought a TB2 equipped display but pickings for USB-C in WQHD or 4K are daily few and far in between.
There is something to be said for waiting for an MBP 'suitable' CPU, but incremental improvements along with price drops one legacy equipment wouldn't be unreasonable. Eventually, someone will do a binary OS X compatibility layer and throw it on top of something like ElementaryOS (OS X 'styled' Linux distro:
https://elementary.io ) - at that point, if it happens, it may become too late for Apple to recover share, at least from a number of folks that use their systems as tools vs fashion statements.