I feel that's a systemic problem with all consumer online-backup software: They often use the barest excuse to not back things up. At best, it's to show a fast progress bar to the average user, and at worst it's to quietly renege on the "unlimited" capacity they promised when they took your money. [1]
Trying to audit—let alone change—the finer details is a pain even for power users, and there's a non-zero risk the GUI is simply lying to everybody while undocumented rules override what you specified.
When I finally switched my default boot to Linux, I found many of those offerings didn't support it, so I wrote some systemd services around Restic + Backblaze B2. It's been a real breath of fresh air: I can tell what's going on, I can set my own snapshot retention rules, and it's an order of magnitude cheaper. [2]
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[1] Along the lines of "We have your My Documents. Oh, you didn't manually add My Videos or My Music for every user? Too bad." Or in some cases, certain big-file extensions are on the ignore list by default for no discernible reason.
[2] Currently a dollar or two a month for ~200gb. It doesn't change very much, and data verification jobs redownload the total amount once a month. I don't backn up anything I could get from elsewhere, like Steam games. Family videos are in the care of different relatives, but I'm looking into changing that.
Yes, you're exactly right. Once they decide not to exclude certain filetypes it puts the burden on the endusers who are unequipped to monitor these changes.
Umm, why didnt you find a GUI manager like Vorta (this one is Borg exclusive IIRC)?
With restic I don't need some kind of special server daemon on the other end, I can point my backup destination to any mountable filesystem, or relatively dumb "bucket" stores like S3 or B2. I like having the sense of options and avoiding lock-in. [1]
As for GUIs in general... Well, like I said, I just finished several years of bad experiences with some proprietary ones, and I wanted to see and choose what was really going on.
At this point, I don't think I'd ever want a GUI beyond a basic status-reporting widget. It's not like I need to regularly micromanage the folder-set, especially when nobody else is going to tweak it by surprise.
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[1] The downside to the dumb-store is a ransomware scenario, where the malware is smart enough to go delete my old snapshots using the same connection/credentials. Enforcing retention policies on the server side necessarily needs a smarter server. B2 might actually have something useful there, but I haven't dug into it.