The problem with this argument is that even if there were multible open source platforms you have "cross platform" problems. Any deversity will result in extra work. So you can either have the one thing to rule them all, or you will have to spend time on doing it for everything.

I admit that IE was shit and it did cost a lot of time. But how about we get over it? They admitied that IE was shitty and now they are doing much better.

There are products from other company that used to be shit, now they are better and people dont still hate on that.

Also, dont think im a idialist who does not remember the past, I was optimizing for IE6 not all that long ago.