First off: clearly you're right. IDE's are very large, featureful software and there are lots of specific tasks they accelerate that you won't find addressed in the common CLI workflow. Finding "references to foo" is a good example.

But here's some stuff Qt Creator can't do (or rather, provides no particular support for -- you can always use it as a text editor, of course): iOS apps; Android apps; sending email automatically; kernel drivers; languages other than C++ or Javascript: Scala, Haskell, TCL, C#, sh, perl, prolog, lisp...; build and deploy a node.js app; fire up an AWS instance; build a binary for an AVR microcontroller and download it to a device; Verilog or VHDL editing/synthesis/verification.

Obviously I could go on and on, but you get the point. The command line environment? Yeah. It "does" all that stuff. And it does it in the same way. A Makefile for your VHDL project is going to look like a Makefile for your web app. The build scripts for your machine learning rig and your AVR hackery work the same way. You write your email in the same editor you use to write your C++ and CoffeeScript (and that you used 20 years ago to write your TCL!).

So sure: if you want to spend your career searching for "foo" in your Qt C++/QML projects, Qt Creator is a great choice. And the next environment you work in will have a new tool, that does all the same boring stuff in mostly the same ways, and you'll need to learn it again. Pick up the command line and get better at it and you'll find you've opened up a much bigger door (and you won't need to learn to use a new editor every year, to boot).

Is it clear now why there are some of us (with decades of make and shell and ssh in our toolbelts) who sit here and scratch our heads at the perpetuation of this nonsense?