This doesn't match my experience at all. I'm writing this from my fairphone 3 purchased in 2019 the day of release. I purchased one for me, one for my wife. I replaced the battery on mine once, my wife never had to change it. Her phone started so show sign of age a few month ago, she switched to the FP6. I will switch to the FP6+ soon as the support come to end this month for the FP3 (I could switch this one to eOS, but performance wise, it's not in it's prime, so I figured I could afford an upgrade after 7 years ^^). I reached out to support quite a few times for my wife or I (for order reasons, issues with operators, bugs, etc) and they have always been excellent for me.
Also as you probably noted, I'm quite enthusiastic about their products and have convinced a bunch of my surrounding to purchase fairphones when they had to change phone (models 3, 4 and 5 so far). I never had any of them tell me they regreted following my recommendation and as far as I know they still use their fairphones.