The story as I remember it went like this: X had a practical monopoly on professional image editing and printing, everything else was for amateurs. (Was that Quark? not sure). Then X did something that pissed off a lot of their users, and within a few months everyone had pivoted to the newcomer, Adobe.
The moral here is that if you've got a monopoly or at least a comfortable majority in an area of software, you shouldn't just be worried about someone else making a better product - switching is effort and people don't like that - you should be very worried about doing something that annoys your existing customers enough that staying but adapting to the new UI / pricing model / etc. is perceived to be as much effort as switching.
(Whoever authorised the new UI for firefox on Android might want to think about this too.)
What I can find is Strategy Letter III, saying that in this situation the best thing for a challenger to do is make sure their product is "backwards" compatible: https://www.joelonsoftware.com/2000/06/03/strategy-letter-ii... Example: How Excel (that Joel was working on at the time) grabbed the market from Lotus 1-2-3.
When people like @prox below say things such as "I switched to Affinity completely, and I also slowly see some people in the industry change.", I'm starting to think that Adobe might be ready for its Lotus 1-2-3 moment. Not letting people install their old Adobe software they've paid for is the best incentive to try out something new that I could think of.