You’ve gotten good advice so far (note that when @jkp says to download the new app and try it that means to do that WITHOUT saying “yes“ to the migration banner in the classic app. Once you choose that banner, you cannot go back).
I don’t know how deep in the weeds you want to go on this topic, but here are the three official threads. They have hundreds of responses on dozens of different issues, but they should give you a comprehensive picture of what’s going on:
Announcement | Changes to our Legacy SmartThings Platform
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Updates to the SmartThings Platform
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New SmartThings Alexa skill (2020)
The short answer is that a lot is changing and a lot more is going to change over the next year. Some of it you will like, some of it you will probably hate, some of it will likely mean you have to redo a lot of your existing set up. But change isn’t just coming: as you’ve noticed, it’s here. 