> Only power users are using this, and they tend towards power user tools.

I have a souped-up zsh config that I clone to all my systems, but I've honestly never seen the point in optimizing my terminal emulator. The shell itself provides the real functionality, and it's cross-platform so by leaning on it I get the same features whether I'm on my KDE desktop, MacBook, or SSH'd in via Termux.

What power user features am I missing by ignoring the emulator and focusing on the shell?

There's some minor things that iTerm2 does that I like:

You can hold down command and click URLs to open them. (You can actually kinda do this in Terminal.app as well by right-clicking a URL and choosing to open it, but it's a bit fiddlier, and I got used to the hover feedback in iTerm2.)

You can click to highlight entire blocks of output from commands, which I sometimes find handy when things feel like they're blending together.

It'll keep a floating copy of the previous command prompt at the top of the screen so you can see what led to whatever output is currently at the top.

None of these are essential, for sure.

Though I don't know how to do the third, Terminal.app supports the first two. Command+double-click opens URLs, and you can select the content of the last command with Edit > Select Between Marks or shift-command-A. (Terminal.app automatically adds a mark each time it detects a new prompt, unless you turn that setting off in Edit > Marks.)

This is actually one of those cases where the ease of doing it makes a real difference to me… iTerm2 does both of those on a single click, and that makes it vastly more likely that I’ll use them. (Completely a matter of taste, I’ll admit.)

Being able to easily set it up so it sends key combinations to remote servers at will (including ctrl/meta/shift combos) was my main reason; this enabled my seamless interactions with remote Emacs servers. 24bit color and italics were the cherry on top. The shells within Emacs have unlimited and easily searchable/editable state. I can log into a shell buffer and copy paste a debug diagnostic output together with the command line; I can quickly create minimal example oneliners iteratively to help debug a problem and paste both input and output at any point in time, including days later. I can search all my open shells (often dozens; sometimes hundreds) for any commands or outputs trivially. This is hard to achieve if the terminal gets in the way to using Emacs in the way I like, when some key combo is impossible to transmit, and I have to rewire things to the minimal common subset that Terminal.app supports and hope that it will not break in the future. Finally, without public source code, I dont think I can truly trust a terminal ever. It feels too personal. Of course apple has control of the hardware and I live with that restriction for parts of my life, but I am less concerned about apple monitoring/intercepting my work, and rather worried about the full number of exploits in the terminal app that remain to be uncovered in the near term. I agree that too many features are a drawback of iterm; at least the code is there and the useful features work well enough.

I no longer use iTerm2 but it has tmux integration built in that's pretty nice if you take the time to set it up properly.

I tried that but I feel the same about that as lolinder says above. Using tmux as normal works better on all my systems, not just the Mac. I just don't see the point to it.

If by “popular” you mean “number of unique users” then almost certainly not.

There are way more power users of macOS who turn to the Terminal because of the beauty of Brew than there are people who switch from Terminal.app.

Thinking there are more people who switched out of Terminal diminishes how massive computing is.