Pure Class rule, after a few campaign its really great !!!! My players don't want to go back

Pure Class Rule

Subclasses are now RPG-related. A player does not even need to choose one.

Starting at level 3, the character can choose any level 3 feature as normal. At the next iteration, such as 

level 6, the character can choose any level 3 or level 6 feature of any of his class subclasses and so on.

Exception: if the new feature is an iteration or improvement of a previous one, the character must have 

the previous feature first. For example, Champion critical hits on 18-20 require the previous critical 

feature on 19-20. The same principle applies to Diviner portent features.

Warlocks still need a Patron, and Paladins still need an Oath. However, a Paladin can take any Oath with 

any level 3 feature, and the same applies to the Warlock and its Patron.

I like the idea of increased flexibility, but this really hurts subclasses that have a lot of 3rd level features. With this rule, you'll basically never be able to get the skill or language or whatever minor buff a subclass gets at 3rd level.