"No framework" has become a reasonable alternative. Bootstrap and others got started because (a) the 12-column grid layout was incredibly nice to work with comp

"No framework" has become a reasonable alternative. Bootstrap and others got started because (a) the 12-column grid layout was incredibly nice to work with compared to the disaster that page layout was before and (b) they provided abstraction over differences in browser implementations. CSS has come a long way since then. Flexbox is possibly a bit more complicated and powerful than .col-xs-12, but not by much. CSS support has largely converged.