IE4 is the first what I would call "recognizably modern" browser, because it's the first browser that has a concept of "reflow" accessible through Javascript. I recall writing some Javascript attached to a button that would add another row to a table, and that new row would have a button in it with attached Javascript that would add a new row. Yeah, it's not how you'd do it today, and I crashed the browser more than once trying to do this sort of thing, but it worked like you expect a browser to work today; a row was added to the table and the page reflowed around it.

Prior to that, nothing worked that way. What limited page modification there was after formatting couldn't ever cause a reflow, and you couldn't even do all the things that couldn't cause a reflow, either. Reflows were simply not a thing through Javascript. (Deferred image loading could cause reflows, and a few other special cases the browser would handle, but you didn't have generalized access to it.)

Netscape tried to compete but they clearly couldn't. They tried to build a "layer" concept, which was ultimate just several chunks of page that could be completely rewritten, but couldn't be reflowed as we'd use the term today. It was a weak concept that was very difficult to use for anything.

IIRC, Netscape qua Netscape never solved this. It was only after Firefox that it could compete. There was a long time where IE was really the only recognizably-modern browser.

It, too, fell behind, its internal architecture becoming simply too limiting. But there was a period of time where it was legitimately the best browser, no matter how anyone may have felt about it.