Sorry, but Modern came out 2 years ago, and Garmin has been supporting both all that time. Plenty of time to report problems and learn your way around modern.
Things are different on modern, but for example, you can control which widget show on your dashboard (with multiple tabs too, if you want), and can remove things you don't want or need quite easily. It starts with the default for what device you use, but you can easily change that and set it up the way you want. And you'll probably find that things you are missing in Modern are there - it's just that there is a different way to get to that data.
As I said, this isn't a sudden change. It's been going on for two years, which is much longer than other companies allow when they are making changes to their websites.