Samsung announced last year that they would no longer host a free Groovy cloud for smartthings, so anything which ran in the cloud, which includes webcore, has to be redone in order to run on the new platform.
Originally the transition was supposed to occur at the end of 2021, but obviously they missed that date, and they haven’t announced a new specific date yet.
Last summer they said that the new rules API would have equal functionality to webcore, but it doesn’t yet. However, it is still in development.
Here’s the official announcement thread:
You can also check the webcore forum to see what other people are planning to do.