But, your friend did throw up their hands and declare his campaign impossible in 5e. Which is why they choose to alter the rules so that their campaign worked.
5e gets a pass that many other games do not (well D&D in general does). And that pass is that the game gets the credit for our work. Here, your friend did work, and changed rules to enable the game they want to play, and you're giving that credit to 5e. Further, you're using your friend work to defend 5e against charges that it doesn't support that kind of play well by saying that if you do the work to take out the parts of 5e that fight against that, then 5e comes through for you and 5e does a great job of doing this kind of play. Yay 5e! It's great that it allows you to fix it, right! I mean... this is primary evidence against your point -- 5e does not support this kind of play, it actively fights against it, but the defense of the 5e system here is to point out how you can ignore the 5e system. That's you, not 5e. That's work you have to do because of 5e. 5e doesn't allow you to make houserules, you have that ability. 5e cannot stop you, just like Monopoly can't stop you from having a rule that Free Parking is a lotto for all payments to the bank to date.