Before adapting to changes in values

Before adapting to changes in values, many prefer to resist, to defend the universally agreed-on principles that have been upheld for centuries.
What is the meaning of the sentence?

“values” means things like social customs or moral principles. When these values change, many people try to resist that change. They defend the old values that they are familiar with.

The sentence would have a more expected meaning if “Before” was changed to “Rather than” or “Instead of”.

I can understand now.

what does ‘universally agreed-on’ mean? if it means “universally acceptable” then my question is-
Are the changed values not acceptable?

“universally agreed-on” has a broadly similar meaning to “universally acceptable”, but agreeing with something is stronger than finding it acceptable.

The changed values may not be acceptable to some people, at least not initially. That is why people resist the change.