Even though most users only upgrade every few years, manufacturers need to release new phones each year so they have something 'new' when you and I decide it's time to upgrade. Also, each company has to 'keep up' - there's something of an arms race going on out there - no one is going to buy a 2-year-old Samsung if there's a new Pixel out there, etc. So sadly, I think we are going to be stuck in this 'several new phones each year' mode.
What I can't comprehend is - why are phones released in different colors, and why do they have a sexy glass back, when ... let's face it ... 95% of people put a case on them? They could save money and put simple plastic on the back, one color, since no one ever looks at that. But yet reviewers talk up the sexy, shiny bodies and the manufacturers keep making them. Am I wrong that 95% of people put a case on a phone? I've dropped every phone I've ever owned multiple times, and whenever I'm tempted to enjoy the 'sexy slim look' of my case-less phone, I'm reminded why I must encase it when it slips through my fingers! Maybe a vendor should try building a decent rugged case into the design, so you don't have to put an after-market case on it? If one were to "design it in", one should be able to come up with a smaller overall footprint. My old Samsung S5 had a removable plastic back (and therefore, replaceable battery - yeay!), and reviewers panned it for looking bad.
And why are Samsung making curved-edge (screen) phones? This makes adding a screen protector more problematic. The only reason I just upgraded my Samsung S7 was because I got a nasty big scratch across the screen - I don't even know how it happened. This seems to be a true triumph of form over substance. It looks sexy in the ads, but does it add any real function?
As I age, my eyesight gets worse so I do appreciate the larger screens now, and I am pleased with the way my S10+ let's me set a fairly large font.
I still find the 'user experience' of browsing on the phone to be awful compared to browsing using my laptop (15.7"). Voice recognition is getting better and better, making the keyboard less and less of an issue.
Fast charging and wireless charging are really cool features I just discovered.
Being able to wirelessly mirror / extend my phone's display to a big screen TV would be a good next step. I know you can do things like that already, but it's not quite mainstream yet.