We have not changed our CSS in a few years until this update, so if your CSS breaks every update, there is something going on with your site not related to Ninja Forms.
We did make some minor structural tweaks to form output in this version, but all classes and ID’s stayed the same and in our testing no major changes were made to form appearance.
Additionally, the most recent 3.0 update requires manual interaction to complete. It also has a one click rollback to avoid any issues impacting the front end of your site so even if changes did somehow break your form output you can instantly restore all forms and data.
If you’ve not reached out to us yet, we have FREE, dedicated support for the plugin which you can contact here: https://ninjaforms.com/