There are plenty of reasons to get rid of Ubuntu, but this isn't one of them.
Before Ubuntu Pro, packages in universe (and multiverse) were not receiving (security) updates at all, unless someone from the community stepped up and maintained the package. Now Canonical provides security updates for universe, for the first time since Ubuntu has been introduced, via Ubuntu Pro, which is free for up to five personal devices and paid for all other use cases.
Debian is actually not that different (anymore). If you read the release notes of Debian 12, you'll notice that quite a few package groups are excluded from guaranteed security updates, just like packages in universe are in Ubuntu. Unlike Ubuntu, Debian doesn't split its package repository by security support though.
This has always been the case with Ubuntu. Ubuntu only ever supported its main repository with security updates. Now they offer (paid) support for the universe repository in addition, which is a bonus for Ubuntu users, as they now have a greater selection of packages with security updates.
If you don't opt-in to use Ubuntu Pro, nothing changes and Ubuntu will be as secure (or insecure) as it has always been. If you disable universe and multiverse you have a Ubuntu system where all packages receive guaranteed security updates for free.
Please note: I still don't recommend Ubuntu due to snapd not supporting third-party repositories, but that's no reason not to get the facts right.
Debian has always been the better choice if you required security updates for the complete package repository.
Personally I have my doubts if Debian actually manages to reliably backport security updates for all its packages. Afterall Eclipse was stuck on version 3.8 for multiple Debian releases due to lack of a maintainer ...
It is entirely untrue. Where as you made the claim, and I am merely calling you a liar while making no claim of my own, it would seem that you must prove your claim with say a sales promotion or some other solicitation plus a credible report that these updates would otherwise exist without the charge from those whose business use case depends upon them.
If you wish to hate upon ubuntu do so, but don't lie about it.
In both Debian and Ubuntu, only the main repo gets official security updates for free. Ubuntu has a paid option for universe whereas Debian doesn't have that option and relies on the package maintainer to provide any updates.
I'd still recommend Debian over Ubuntu though, for various reasons.
Package maintainers can be slow to update packages though. Debian have a separate security team that get patches out ASAP, and those packages go into a separate security repo. I imagine Ubuntu does the same. It's that security team that only deals with "official" packages, meaning anything that's not in contrib, non-free, or non-free-firmware.
What you're paying extra for are timely security updates for community-maintained packages that aren't an official part of the OS. Debian doesn't provide that for free either. Debian doesnt provide it at all since they don't have any paid options.
No. All the official packages in the main repo get security updates from the Debian security team.
Only the packages in contrib, non-free and non-free-firmware don't have official security updates and rely on the package maintainers. These are not considered part of the Debian distro, and I don't even have them enabled on my servers.
Out-of-the-box, Debian only enables the main repo, plus the non-free-firmware one if any of your devices require it (e.g. Nvidia graphics, Realtek Bluetooth, etc). You have to manually enable contrib and non-free, and by doing that, it's assumed you know what you're doing.
In the case of non-free and non-free-firmware, they can be closed source software (like the Nvidia drivers) or have a non-open-source license that doesn't allow distributing modified versions. In those cases, the Debian team is unable to patch them even if they wanted to.