Bell Labs was great at invention, but AT&T had little incentive to deliver innovation to its rank-and-file customers. My parents had the same landline phone for 20 years, and were paying C&P Tel. $5 a month for it until the law changed allowing them to buy their own phone. And Ma Bell wasn’t necessarily the worst of the phone monopolies. I lived in Durham, NC in the early 1970s which was “served” by GTE at the time. Now, *that* was third-world phone service.
Only people in our modern world of disposable junk could think that having a piece of equipment work for 20 years is a bad thing. Meanwhile the backbone that phone connected to probably went through 4 or 5 major upgrades. They delivered tons of innovations, you just never got see them as quietly your phone system became more reliable while handling drastic increases of traffic.