I don't think things have changed that much in the time I've been doing it (roughly 20 years). Tools have evolved and new things were added but the core workflow of a developer has more or less stayed the same.
I also wonder what those people have been doing all this time... I also have been mostly working as a developer for about 20 years and I don't think much has changed at all.
I also don't feel less productive or lacking in anything compared to the newer developers I know (including some LLM users) so I don't think I am obsolete either.
I don't think that's true, at least for everywhere I've worked.
Agile has completely changed things, for better or for worse.
Being a SWE today is nothing like 30 years ago, for me. I much preferred the earlier days as well, as it felt far more engineered and considered as opposed to much of the MVP 'productivity' of today.