I can hopefully clear some stuff up for you. I know change is hard to deal with but we are making this updates for the site and communities health in the long run. Yes there are advertisers but they pay for the staff support, servers costs, and upgrade likes this. Without them, you would not be able to access the site nor keep it running smoothly.
My main focus and duty as a Community Manager is to keep our sites active, happy, and work with the community to make the best experience possible for the end users.
In regards to the "if it ain't broke don't fix it"
quote I see 20x a day on the 300+ sites I have upgraded. Unfortunately, the site was broke in the eyes of Google's new mobile rules and was missing many features that most sites now offer. Websites have to upgrade, update, and evolve to stay relevant. (see links below). Without updates they fall behind, come up less in search, users are unable to access in mobile, and it will end up choking out the site.
Googles new rules for websites: https://support.google.com/adsense/answer/6196932?hl=en
Here is a site not touched since 1996 as an example of how far the web has come: Space Jam
All major players will be updating sites, We built out this custom template 3 years ago and have been continuously improving it ever since.
I hope some of this clears up the purpose behind the updates and changes, we would not be investing all these resources to make the site worse or to alienate our community.
Feel free to reach out with any other questions.