Maybe this comment was meant to be sarcastic, but the version number is not an indication of progress as it was with prior development. When Chrome went all nutty with frequent new version numbers, Mozilla followed suit.
You know that there is a point to it, right? Now there are always 4 versions: fresh nightly builds, dev, beta, and stable. Every ~6 weeks dev becomes beta and beta becomes the new stable version. This way you get a higher degree of parallelization. There is no global feature or whatever freeze. New stuff is added all the time.
The version number is now basically just a step counter.
I know you tried to be funny, but this "150" actually means something very specific. It's +125 of those steps.
That's way more meaningful than +7 major releases. Just look at other software. Sometimes it takes 1 year. Sometimes 6 or even longer. Sometimes the changes are very minor or purely cosmetic. Sometimes the changes are very drastic. Sometimes it's even a complete rewrite.
I don't see how that's any better. Basically, it just means that someone thought it would be a good idea to increase the major number by one.
What I said doesn't imply that I find the idea silly, but "Firefox 150" does indeed sound silly to me. However, what you say seems to hinge on the idea that each of Firefox's steps are consistent in their impact. Is that true?
Of course there is some variation. There are always some bigger features which take their sweet time. However, there is always a constant stream of smaller fixes and improvements.
Also, if there are ~86 releases per decade, those features and improvements are of course far more evenly spread compared to some product which only released 4 versions in the same time span. (IE6 was released in 2001 and IE9 in 2011.)
The version number is now basically just a step counter.