The data for this chart was generated from the PGstats backend and looks at 38,956 games played since Patch 9.0.0 and Steve dropped on October 13th:
click to expand. scroll to the bottom for expanded versions of two of the most clustered areas of the chart.
Win rates range from 60.9% (Simon, top left) to Sheik (36.3 percent, bottom left). With Simon and Richter combined, their win rate falls to 59.1%, just a hair behind Snake (59.4 percent, top right).
Usage rates range from 2.8% (Palutena, far right) to 0.17% (Daisy, far left). With Daisy and Peach's usage rates combined, the least used character becomes Rosalina (0.22%). In patch 11.0.0 alone, Pyra & Mythra's usage rates balloon to a whopping 9.1% (used 1,135 out of 12,470 opportunities). While it's not quite as extreme, Sephiroth is by far the most used character if we look at things from only Patch 10.0 onward, where he has been used 3.7 percent of the time (used 1,881 times out of 50,380 opportunities).
The absurdly high usage rates of the Aegis and Sephiroth combined with their mediocre win rates points to something I can currently only conceive of as the "cool DLC effect." See also Joker, who remains one of the most used characters online despite poor results and a general consensus that the character is much more effective offline. Similar takes have been dropped about the Aegis and Sephiroth, and while it's harder to say for sure if that's the case with them as compared to Joker, who has dominated offline events, it certainly seems like we're seeing the same issues with the new DLC.
I also, though, think these win rates overstate the degree to which these characters are "bad online." There's also a certain portion of the player bases for these characters that is willing to lose with them that would not be willing to lose with other characters, particularly those in the top left corner of this graphic, where the "lame projectile zoners" live. Some of that might just be the process of learning a new character, but the fact that Joker still sits at a 43 percent win rate well after his release suggests that's not the only issue. Perhaps people are more willing to lose and experiment with a character that the community has blessed as "cool;" perhaps people are sticking with Joker in hopes that their practice will translate to offline; and perhaps people still believe Joker is top-tier online. Most likely, it's some combination of the three.
It likely comes as no surprise that Steve (2.3% usage, 54% win rate) and Min-Min (1.7% usage, 58% win rate) have joined the ranks of gatekeeper characters that includes ROB (2.1% usage, 57% win rate), and Snake (2.3% usage, 59% win rate). Even though their win rates are lower (which I hypothesize is partly due to a similar but not as strong effect as we've seen with the DLC mentioned above), I would also include Ness (2.8% usage, 52% win rate), Bowser (2.8% usage, 49% win rate) and Palutena (2.8% usage, 52% win rate) in this list.
To a lesser degree, it is critical to learn matchups like Donkey Kong (2.1% usage, 53% win rate), Terry (2.1% usage, 52% win rate) and Yoshi (2% usage, 52% win rate), with King DeDeDe (1.5% usage, 56% win rate) and Luigi (1.7% usage, 54% win rate) lurking as slightly less common but still plenty capable wi-fi gatekeepers.
Simon, Richter, Wii Fit Trainer, Mii Gunner, Mii Swordfighter, Duck Hunt and Ice Climbers all have a pick rate under 1.0% despite win rates of 55% or better. This group is basically heavy zoners and also Ice Climbers. The heavy zoners thriving on Wi-Fi should come as no surprise. It's incredibly difficult to properly navigate projectile minefields like those the Belmonts or Duck Hunt can throw at you due to the committal nature of shield and shield dash in Smash Ultimate; adding Wi-Fi lag to the situation just makes things worse. With Ice Climbers, I find it hard to say if this is them benefiting from online play or matchup inexperience in general; with a pick rate of just 0.3 percent, you're not getting much of a chance to learn that matchup.
Lucario, Corrin, Marth, Mewtwo, Dark Pit, Rosalina and Sheik all live in what I call the Zone of Despair, with a usage rate under half of average (0.6% or less) and a win rate of 42% or worse. These characters are a combination of mid-tier or worse offline and don't benefit from the mechanical changes of online play.