Theme CSS conflict with wp-core-ui

After recent updates I am having all sorts of conflict with the styling of core WordPress elements on the admin side. I have custom CSS for my theme in which I am targeting specific buttons, but I had to go with a global “.btn” for it to work on all elements. For the past couple of years, this was never a conflict. But after updates this week I am seeing all sorts of core elements when in “Edit” mode on the admin side, styled just like the front-end buttons. Can you help me determine why this is happening?

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