One of Adobe's (and a few others) biggest failure points. They've never completely re-writen their core programs to meet demands, and current technology, they just keep adding, and adding, and adding code and features, which isn't a long term solution to keep software of any type stable. Microsoft had a hard time learning that lesson too.
While that is true on one hand, the downside is that customers also won't tolerate the issues that arise with such a refactor and to do it correctly. Also compound now that we have this "re-write it in Rust" (not a fan of Rust, but that's another topic) or in some other "memory safe" (but not yet truly proven on this scale) language, which is going to have an pressure on dev time.
I remember when Ai got a
larger artboard (not infinite artboard) and how people felt that it was a hacky solution (I dropped Adobe long before they did that) and yes that will happen. It is huge tech debt, no doubt, but if they tried to refactor to deliver that feature, it will be no bueno for customers in the near term and for Adobe as well. Customers, for the most part, are more about near term solutions, not long term ones. Why partly SaaS has worked for Adobe, when overall, it's a bad model for customers.
Ideally, they would run 2 repos, one with the newer "modern" codebase and the other would be legacy to keep in maintenance mode until the "modern" one could go live. But would customers really handle a SaaS model to where it's more upkeep and not really getting the latest and greatest anymore, until Adobe was able to deliver on the "modern" one?
No matter what, it's Sophie's Choice.