I learned the basics in maybe a day almost 20 years ago now. I could make a page template with PHP and style that in maybe a day. This was back when IE6 was dominate, I don't think Firebug was even a thing.
At that time I was a novice, didn't know what a debugger was (I printed everything out the the console / page) and didn't know what an IDE was (I think I was using Notepad++). I managed this feat by following the tutorial.
The biggest problem I had was that I couldn't understand why centre, and colour didn't work. Once I realised that I had to spell everything in American English, that problem quickly went away.
I too learned the basics of CSS back in the IE6 era, and I had no trouble following the steps of the tutorials, using similarly primitive tools. If I'd had an experience like yours, I suppose my career might have gone in a different direction. Instead, though, as soon as I tried to take what I thought I had learned from those tutorials and make something of my own, I smashed into a wall of chaos; nothing seemed to be predictable. I knew the browser could do what I was imagining, because I had been making it do that for years already via tables and repeating GIFs and all that, but trying to do it with CSS got me nowhere.