Nonsense. You're still graded as a team if you're playing in a party. But now, if you're the only good player on a team of useless randoms, you can avoid losing points just because the matchmaking is lousy.
Frequently being the top player of either team but still losing ranking points is a big part of what lead me to quitting the game entirely. Someone who plays well but is unlucky when it comes to getting matched with competent teammates doesn't deserve to be stuck in silver or gold forever.
Oh, I actually missed that line about it being graded for your party. That's good, though it means I won't want to play with bad players...
As for solo qeueing though, it sounds like an absolute nightmare. Have fun qeueing with randoms all scavenging after KOs just to boost their SPM. All running staff and marking because support score is overpowered in regards to how it influences SPM.
It's a team orientated game, and playing with a group of players all fighting for their own individual performance, isn't going to bring your team anywhere closer to the unified goal.
Also for the people complaining about not being able to enter a solo queue playlist, the note from ND basically tells solo queuers to join a team.
"Playing with friends is the best way to succeed on your journey towards Master. To encourage this, there are no party restrictions to play Ranked together. Play as a team, communicate often and you will prevail."
I find that amusing, as that's my own perspective on the matter. You can't expect to achieve a high ranking in a team based game by being isolated away from the team based elements in your own queue. If you want to do well, you're going to need to join a party. Even in a party your individual score isn't enable you to keep increasing when you hit platinum / diamond. In a game full of parties, regardless of how good you are, you're not going to win even 40% of your matches at that level when solo queueing.