Yes, of course I know that.
The problem is time - other ways of getting XP are more time consuming and even for them XP gain is not shared (or is distribution buggy, sometimes I get them and sometimes I don’t) - so in a party you probably “steal” XP from each other.

The new system has advantages and disadvantages but the disadvantages outweigh the advantages, especially in coop, not to mention that the system still has bugs with what to accept and what not to accept for completed challenges