So don't buy one then. Unlike 6 years ago, there are now several PHEV SUVs on the market to choose from if you're buying new. I'm sure they all have their issues and things that don't suit everyone.
You did the right thing for doing your research before spending a lot of money. I did the same, plus a lot of research on the forums for the Audi A3 e-tron and BMW 225xi which were options in my price range. And I found things I didn't like about the A3 on the Audi forums that some members were getting angry and upset about and others were saying it wasn't really an issue if you understood what was going on. I actually decided the specific issue (not actually an EV related one) probably wouldn't be a problem for how I intended to use the car, but ruled it out simply based on the boot not being big enough. I ruled out the BMW based on other factors before I got into too many specifics.
Ultimately if you push any battery hard it'll degrade faster. So on a PHEV of any make, lots of rapid charging, lots of high load driving with it forced into EV mode (when the car would prefer to use the engine) and lots fully discharging and recharging will all affect the capacity. It's no different to a petrol car - accelerate to the red line all the time, turn if off when it's very hot, drive it hard when it's cold etc will all mean the engine sufferes. Look after a BEV or PHEV and it'll last and perform well, just like looking after a petrol or diesel engine. Whether Mitsubishi could make it perform better isn't that relevant as far as I'm concerned, it is what it is and if you don't like it, don't buy it.
I came to the conclusion that the battery degradation on 2013-2016 models was nothing to worry about so bought a second hand pre-facelift 2015 model for about twice what I'd normally spend on a car (offset by not having to pay car tax and the saving in fuel). It's just approaching 60,000 miles and the estimated range after a change is always around 24 miles, which drops to about 22 once I've driven about 500 metres. I can still do a week of commuting to the railway station without using any petrol. That to me means the car is doing what I bought it for. I don't obsess about it losing 0.1Ah of capacity, because I don't find it useful to do that sort of thing. I want the car to get me to work cheaply and cleanly, and be able to drive to the other end of the country at weekends if I want to. It does that and I don't expect that to change in the five years or so I intend to own it.
I find that the football team I support tells everyone that they can win games. In reality that's proved not to be the case this year. Don't always assume that anyone selling something will tell you anything other than what you want to hear. Do your independent research and draw your own conclusions. If you find something you don't like, rule it out and look at another possibility. (To be honest, Chesterfield Football Club have been pretty rubbish for a while).