As a Linux user, I disagree. It's not quite the same. Yes, I could recompile my kernel if I wanted to. I can recompile most of userspace too. But it's a hassle, especially if you want to diverge from upstream, and maintain that divergence on a long-term basis.
You can do some fun hacks with LD_PRELOAD et al, but it's nowhere near the degree of flexibility and ease of access of browser extensions.
I am allowed to modify all the software as I see fit (and that's excellent), but the friction of actually doing so is (comparatively) high.
You raise an important issue around persistence of state.
The question isn't whether you need to recompile source, change config
files, download application plugins or set-up a bunch of check-boxes
in a nice GUI.
It's whether you can trust those settings to stick.
I've lost count of people telling me that phone settings I suggested
simply "reverted" or somehow turned themselves back on/off.
Even some Linux distros that use Snap alongside auto-updates etc are
really quite sneaky.
But to my mind web browsers (and I include all of them, Chrome,
Firefox or whatever) are utterly treacherous.
Any careful security stance requires constantly checking and
re-checking that policies are still in effect.
I feel gentoo reduces that hassle a fair amount since you can just toss the patches in and the distro pulls them in on updates. So long as you're not messing with APIs it's not too bad in terms of bitrot.
... I suppose you could do the same thing with debian too. You'd just need to maintain an overlay repo that rebuilds off the upstream deb sources for the packages you touched.
At that point you're pretty much doing the same thing distro's volunteer maintainer is doing. Take an upstream package, add tweaks, rebuild them automatically with tweaks on the next upstream release.
It's similar with NixOS, patching a package is just adding a few lines in a persistent (and generally short) config file. You "only" pay for that patch by having to update it for newer versions and by compile time.
The developer experience isn't as good as browser extensions yet, though. Iterating on a patch means downloading that package to a local directory and building it there, which won't be enough for, say, patches to system libraries. You have to actually apply the system configuration for that, which means recompiling.
I should maybe give Gentoo a second try. I last tried it on a dual-core thinkpad and it was a pretty miserable experience due to the long compile times. These days I have fast computers, and I hear Gentoo even started shipping binaries recently.
I have a huge amount of respect for the work distro maintainers do. It's not especially fun or glamorous work, and many are unaware that it even happens, but it's essential.
What has compiling the kernel to do with it, its about the fact that Linux let you control ever single aspect of your OS and tweak it to your liking. Its a pretty good example of what shows you how it is to control your PC, more so then browser extensions. Just look at what a pain in the ass it is to remove Edge from windows, even now the EU has mandated it, its still a 10+ step guide that requires some tool from Github ... and b4 that you could not even to that. Your start menu in win11 is polluted with "news" and Bing AI crap ... with no simple way to just disable it. If you use Linux you are in control and there are no annoyances and almost no proprietary code from the very start.
You have endless different Desktop Endorsements ... Linux offer way more control over the OS then any browser extensions do. Firefox killed the system where you could more modify the look of the Browser, I do not mind, but I am still making this point when we talk about feeling in control.
As a Linux user, I disagree. It's not quite the same. Yes, I could recompile my kernel if I wanted to. I can recompile most of userspace too. But it's a hassle, especially if you want to diverge from upstream, and maintain that divergence on a long-term basis.
You can do some fun hacks with LD_PRELOAD et al, but it's nowhere near the degree of flexibility and ease of access of browser extensions.
I am allowed to modify all the software as I see fit (and that's excellent), but the friction of actually doing so is (comparatively) high.