Mint is preconfigured Ubuntu that avoids a few user-hostile choices. Techies talking about choosing a Linux seem to careen between Ubuntu/Mint dead-simple consumer stuff and then the other way to Arch, when they decide that they're too expert for Ubuntu (then to Macs, after they have one very rough day with Arch.) Debian is nice, and simple. Takes a little bit of configuring to taste, but configuring the next Debian how you like isn't going to be much different that configuring the last Debian how you liked. Keep a text file that reminds you of any weird config changes you make and why.
It also upgrades in place nicely. Excellent distro for Ubuntu and Mint to base themselves in.
Installing Arch with the cli installer [1] is pretty straightforward these days. It only becomes a lot more work if you have very specific preferences on partition layouts, filesystems and bootloaders. In my experience, changing these things on Ubuntu was even more difficult and less documented.
I haven't tried Arch, but in my experience changing those things in Ubuntu setup is simple and can be done in the GUI installer - I do it every fresh install. I haven't tried changing the bootloader; haven't had the need to.
There are many configurations that aren't (easily) possible with the GUI. The average user isn't going to care if they use LVM on LUKS or LUKS on LVM, but if you do, Arch makes it easy.
I personally prefer using EFISTUB instead of a bootloader, and this was very difficult to do on Ubuntu last time I tried.
As Ubuntu gradually snapifies more and more stuff, Mint is either going to start falling behind or have to redo Ubuntu's packages (reducing any benefits of the Ubuntu heritage...).
Mint might be an OK stopgap, but I wouldn't call it a long-term solution to Ubuntu's snap infestation. Just like you won't get a good OS by playing whack-a-mole with the various workarounds you have to do to avoid Windows' latest user-hostile bullshit.
Yeah, setting up arch for the first time takes time. For newbie users it is definitely not appealing process, and also I would not recommend it. It's not a long process, but you do everything yourself and all this in the terminal (no GUI installer).
I learned a lot about linux when I decided to try Arch. And as OP, I also never looked back :)
My experience with Arch (which I tried after I'd used Linux Mint) was that for the first few weeks I was constantly consulting the Arch Linux Wiki to get anything done. -- I mean, yes, the emphasis is on "learned a lot".
It also upgrades in place nicely. Excellent distro for Ubuntu and Mint to base themselves in.