I haven't used Powershell since Windows 7, but at least back then it was super slow to start. cmd.exe opens immediately, like a normal terminal emulator. Powershell took several seconds to open.
At least for me, if I'm opening the command line it's to get something done quicker and easier than I could with the GUI. Powershell wasn't that, at least on Windows 7.
Just for your reference, I've got Windows 10 and Powershell 5.1 running on an SSD (probably the only hardware that matters for program launch, really).
I can hit Win-X-I and start typing commands as fast as possible and Powershell is up instantly and I've never missed initial characters on a command. For interactive use, it's always there and up quickly.
This is in contrast to the typical start menu search which takes about a second before it registers keystrokes and I'm always searching for something missing the first few letters of the file or executable name.
Windows 7 shipped with PowerShell v2. So yes, back then it was slow. It's not anymore.
Side note: A terminal emulator is completely different from a shell (and on Windows (prior to 10 at least) there wasn't such a thing, but rather the console, which did not emulate a terminal).
At least for me, if I'm opening the command line it's to get something done quicker and easier than I could with the GUI. Powershell wasn't that, at least on Windows 7.