Agreed, the last great upgrade was the SSD. After that, for people using their laptops as non-intensive consumer devices, what else do they need?
For a few more years, the decreasing costs of SSDs were giving incentive but yes, once you have that, what incentive remains? The high resolution screen is still more trouble than advantage.
I was purchasing newer and newer ThinkPads for a few more years, until I could put 16GB (for a sw developer, having lots of RAM is helpful) in a 14" model, then stopped at the T420 in 2011 and that's the end of laptops for me for the foreseeable future.
And perhaps increased CPU performance because I like short compile times please.