Kitkat(Android 4.4) is 10 years old and I have experience with it. You can't update Signal since last year and you can't use it anymore since soon after that. Whatsapp didn't work anymore after May. And most(all?) of the phones bought 10 years ago didn't have kitkat yet.
Those two are the apps that survived the longest (Try getting any matrix client to work on it). Others broke sooner, most of them because the app developer has to enable TLS1.2 to be able to use it for HTTP APIs and many web servers disabled responding to older versions a while ago. Firefox (the one which allowed all extensions) still works. Great! But I can't message anyone anymore. On a phone.
TBH I put most of the blame here on app developers (supporting older stuff is not that hard) and some of it on the device manufacturers.
Those two are the apps that survived the longest (Try getting any matrix client to work on it). Others broke sooner, most of them because the app developer has to enable TLS1.2 to be able to use it for HTTP APIs and many web servers disabled responding to older versions a while ago. Firefox (the one which allowed all extensions) still works. Great! But I can't message anyone anymore. On a phone.
TBH I put most of the blame here on app developers (supporting older stuff is not that hard) and some of it on the device manufacturers.