I think even from 6 also not much improvement. The headphone jack is gone, camera only small improvement unless you go for 7+. Screen is the same resolution, speed also not much difference and still have to get used to the new home button.
Best improvement would be battery life but then still need to charge once a day so not much impact on daily life also.
Yes, iPhone 7 is not much improved from the 6s but until competitors actually match it, iPhone will always be on top. Just look at Note 7 vs iPhone 7+. Speed is miles away. iPhone 7 is the fastest phone in the market which even best the MacBook Air.
Display Mate has already proven that the resolution of the display is not everything. iPhone 7 has the best LCD ever, even better than all the TV panels tested by DM. Going to 2K resolution will waste even more battery with negligible difference.
iPhone has always been about speed, stability, reliability and user friendliness. Their specs is not always the higher end, but they will always be better than their competitors due to hardware and software integration.
Haters will always hate but the test has shown the superiority of the iPhone 7. Even though iPhone 7 has only a rating of IP67, but test has shown that it can stay longer and deeper in water as compared with a Samsung phone which has a rating of IP68.
Apple has always been very humble with their specs and iPhone always outperform what the specs has stated.
All these claims are not by me anyway. All the test can be found in youtube and online. I am also not an apple fanatic but I really admire Apple as a company and how they always break sales record for their iPhone.