Immortal
Arcane
It's your choice whether you want to see the glass as half-empty or half-full.
Is it really a problem that you can group with your friends regardless of your levels or is this a solution to the problem? I grouped with a level 25 when I was level 13 and it was great. He wasn't overpowered, I wasn't underpowered. It was just like I was playing a brawler like Double Dragon at the arcades and someone else joined the game.
All the progression systems still function perfectly. You don't get any less XP because you're partied with a high level player. You both get your own drops appropriate for your level. You don't feel weaker the higher level you are until your items are getting old but the system to extract the legendary aspect from an item then attach it to a new one means you can keep your favourite item for quite a long time. It does all scale but it seems to be done really well.
Your argument is basically "This design lets me play with my friend.. there's no downsides so stop complaining!"
But there is a huge downside to this.
There's something cool about going somewhere you shouldn't .. overcoming or getting your ass handed to you.. bringing higher level friends or getting stronger yourself.
I have fond memories having my more powerful friends help me through difficult content or me helping my friends through content they shouldn't be in.
Rushing people through acts or power leveling them..
All of this is gone.
You've even lost all motivation to catch up to a friend or a group of friends who are ahead of you because you joined a week late, these motivations to achieve something are important.. or pausing your miller box loot hunt to go help a friend in a similar boat.
Now, everything is catered and scaled to your level at all times so you are never inconvenienced. It's so gay and boring.
Frankly - I completely and wholeheartedly reject the "I work 30 hours a day with 12 kids so I can't be inconvenienced at all in my video games! Cater to me!" type arguments - it's literally killing game enjoyment for everyone else.