Honestly I don't want new features on Chrome or Firefox. They are fine how they are -- though I wish Mozilla would take out the value-added services they just had to add. Release security updates and that's it
They could have improved on it without forcing people to use another Google service too.
Early adopters would flock to it, the comfortable majority would happily stick with what they know. Win win.
Also they kind of just did what you suggested with Duo,Allo and Hangouts.
To play the devil's advocate, couldn't you argue that the reason the take-rate seems high is because only the people that want change are going to use the disrupter's thing, whereas those people represent a very small minority of people using the existing, uninnovative product?
For example, consider what Mozilla did when they first came out with Firefox. They didn't replace the main Mozilla browser; they built a new browser and offered it as an alternative. It took a long time for everyone to switch over, and that's completely OK.
Opera has a well established history of innovating web browsing. So many features we consider normal and must-have in modern browsers were pioneered by Opera. The innovation kind of stopped and a lot of features disappeared when they fired the Presto team and switched to webkit, unfortunately.
Google on the other hand, has a well established history of developing a pretty great idea and then at some point begin making it shittier with each update.
This may be a bias of an old Opera fanboy / IMHO; If you consider innovative features, between Opera (frozen just before they ditched Presto), versus where Chrome has innovated and been developed to today--Developer tooling maybe, but from a user point of view? Nowhere even close. Especially if you consider what was taken away (but then, the entire Presto engine and many of its unique features were taken away too).
Opera has had more of a "Yes, and" approach to innovation, but still they (barely) managed to avoid the "kitchen sink" problem. Old features almost never went away. I used to think the built-in torrent client was unnecessary bloat, but in hindsight was that really a bad idea? Main problem was torrent protocol itself was a bit heavy for computers at the time, making it feel bloaty. Unlike the built in IRC client, which was just another lightweight browser tab unlike Chrome (or Firefox) could ever manage. Still, Opera was also famous for it's tiny executable size.
I think this is a poor example, this does nothing to make the browser better at browsing the web. It's just a feature no one asked for, that has loads of alternatives already. Why do I need video calling built in?
Remember when Chrome tried to innovate with how we use bookmarks? [1]
People cry out for innovation, but then freak out when said innovation happens. This is why disrupters are so successful - they can do something crazy and people will try it out and think - this is amazing. Because the mindset/psychology is that this is something new. But the market leader implements exactly the same thing and people won't give it a chance because it's a change and they can't handle change.
But I actually disagree that they are stagnant. They may be hesitant to change the UI, but there is a lot happening under the hood to make them more secure, faster, standards compliant, stable etc.
[1] http://www.omgchrome.com/new-bookmark-manager-chrome-disable...
Edit - Adding an example of recent Firefox innovation being rejected https://support.mozilla.org/en-US/kb/hello-status