> Modems are speed limited by networks which evolve on a MUCH slower timescale
While true, at some point networks do catch up, and many people hang on to their phones for several years at this point. If that's the case, whether having a better modem makes a difference in the end depends on which dimension of "faster" you're looking at:
Just using more and more Hz of spectrum on a single device does indeed not help anything other than peak speeds in empty cells (something I personally don't care about in the slightest in a phone), but being able to deliver more bit/Hz/s (through spatial multiplexing, better beamforming etc.) does eventually benefit everyone in congested/spectrum-limited situations.
While true, at some point networks do catch up, and many people hang on to their phones for several years at this point. If that's the case, whether having a better modem makes a difference in the end depends on which dimension of "faster" you're looking at:
Just using more and more Hz of spectrum on a single device does indeed not help anything other than peak speeds in empty cells (something I personally don't care about in the slightest in a phone), but being able to deliver more bit/Hz/s (through spatial multiplexing, better beamforming etc.) does eventually benefit everyone in congested/spectrum-limited situations.