There is a really good center of the road set of web browser features which all modern browsers support. This was not the case when IE was big, in order to make nice, functional web pages you needed to either give up supporting one platform or the other or you needed to spend tons of time and energy making 2 (or 3) pathways for extremely basic features.
If one browser is 1 year or two behind standards generally doesn't matter because as web developers we need to support 3-4+ year old browsers regardless. The truly crappy thing about IE was that Microsoft had zero commitment to web standards at all and many things they did outright contradicted them. Since IE had such massive market presence they undermined the standards process for more than a decade.