The standards addressed a lot of the pains and struggles we had with floats/clearfix etc. This was challenging but nothing im comparison to supporting IE 6-9, FF, Safari, Opra etc. at the time. Also hacking in JavaScript added to the complexity.
Nowadays I can do with 10 lines of grid and flex what great CSS frameworks like Bootstrap abstracted away behind 1000th of lines of code.
Also testing is way easier, since browser vendors follow standards and there is chromium everywhere.
Earlier we did a lot of div soup, I remember fondly CSS zen garden as well as OneDiv.
Awesome times to be a web dev, you work on products (PWAs!) not on browser hacks.
My 2 cents.