No, it's not something specific to the early days. It's just the way things are, if you don't constantly stay on top of it. Software rarely ossifies; it atrophies. Can happen at any time, in any ecosystem. Even happens to really old legacy systems. Probably much worse, in fact, as they tend to have _a lot_ of code to maintain, and they need massive and constant upgrading, to stay working. That's actually where most of the "steady jobs" are, in IT. Revamping COBOL and Powerbuilder stuff, and etc.

I remember the move from MS-DOS and mainframes to Windows and PCs, for instance, and then the leap to the Internet. And then you get your SaaS going, and it still doesn't end. From PHP forms to Angular JS, to React, to Svelte. Get your RDB setup and then it's all NoSQL and... You have to constantly run, just to stay in place. The bigger and more mature your system is, the more work it is to stay in place.