If they're not using fzf, ctags or LSP at all, sure. But find and grep absolutely have their place, and I tend to use them even when using IntelliJ/VSCode.
Yes, no one said find or grep are useless, far from it. The original premise was people using grep to look for a function in a code base, or find to get to a file (presumably to get to an include file or imported module by name). And they are definitely sub optimal for this - as you mention, even outside of an IDE, there are plenty of better tools to integrate with vim or nano or ed (the standard text editor!) or whatever you prefer.
