You find yourself having to do "Right click > inspect" a whole lot less often to figure out what's going on
Tailwind is not easier than a custom internal design system either, as that has been tailored to your company and the maintenance of that system is integral to your design team. You might think that offloading to Tailwind is better, but you're just doubling up duties because someone internally is going to have to customize away from the defaults.
Tailwind can be easier to maintain than similar libraries. After trying most of these, I can't say whether that actually shows itself during development. I suppose if one was exclusively used to Vue or was brought up in the world of overzealous BEM, Tailwind might seem easier/refreshing. But if you've worked with Bootstrap or its alternatives (of the time), Tailwind isn't much different and can feel like a step back when you now have to rely on additional libraries like Konsta, Daisy, or Tailwind UI to create premade components for you.
Your example confuses me too, because why wouldn't your devtools be open anyways? You're in development so use the tools you have to make your job less of a guessing game. I guess what you say might be true, you can load a page and just tell a component has a margin right but you're going to be opening the devtools anyways to double check.
I still think Tailwind is great for solo devs, it's a design system with sane defaults they can rely on and get something in production very fast. Every other reason I've seen Tailwind devs give winds up confusing me about how they're actually working, or if they've ever bothered with anything else.
Instead I find myself going to the Tailwind docs to find out how they renamed this random css property.
But it’s still better than plain CSS.