Except regular people want to be able to watch a video without screen tearing, or use their nice new monitor at a resolution that suits their needs without the UI being tiny/huge. It doesn't matter if the user experience is consistent, if it is consistently not what they need, they'll still switch away.

Not breaking stuff is a great goal, but it is a trade off, there is a cost to supporting the old, and it isn't always worth paying. Just sounds like your priorities don't line up with the people actually paying and doing the work. Your attempts to convince that it's a better option by telling them they are stupid actually are misguided if you think that'll actually work.