Personally, I prefer bookmarklets over extensions and Tampermonkey.
They work the same on Desktop, Android and iOS. So I can write my bookmarklet once and use it everywhere. Without installing anything. I also like that bookmarklets only kick in when you click on them. Although some might find that too much work, it feels natural to me. It is already in my muscle memory, to click an "Increase Fontsize" bookmarklet when I start to read through a thread on Hacker News on a mobile device, for example.
They work the same on Desktop, Android and iOS. So I can write my bookmarklet once and use it everywhere. Without installing anything. I also like that bookmarklets only kick in when you click on them. Although some might find that too much work, it feels natural to me. It is already in my muscle memory, to click an "Increase Fontsize" bookmarklet when I start to read through a thread on Hacker News on a mobile device, for example.