I was thinking the same thing. I've actually been thinking G&W might be top 5 for a while. The character is light, sure, but he also has some of the best moves in the game, and is a character that is relativitely easy to play, which makes him more consistent than more complex characters like Joker and Peach.
Miya in 2023 has (based on ssbwiki): 15 1st places, 4 2nd places, 4 3rc places, 1 4th place (Seibugeki 14), 1 5th place (Battle of BC 5), 1 7th place (Kagaribi 10), 1 13th place (Umebura SP 9), and 1 49th place (Kagaribi 9). Also an online tournament win which I don't count since it's online. 15/28 are 1st places, and only 5/28 outside of top 3. (Though I did include the TOKYO SMASH BOOT CAMP which he won but it didn't count for ranking so I suppose you should probably discount that win)
In comparison, MkLeo has 3 1st places, 1 2nd place (MAJOR UPSET), 0 3rd, 2 4th, 1 5th (Crown the Third), 1 7th (Delfino Maza 2023), 3 9th, 1 13th (Battle of BC 5). 3/15 1st places, 8/15 outside of top 3.
Maister's consistency is not as good (probably because he's not a top 10 player in the world). His 2023: 3 1st places (regionals and superregionals, no major wins), 0 2nd, 2 3rd (superregionals), 1 4th (Collision 2023, supermajor), 1 5th (Battle of BC 5, supermajor), 0 7th 3 9ths (two supermajors and one major), 1 13th (Crown the Third, supermajor), 1 25th (GENESIS 9, supermajor). Still good and I could see him being a top 20 contender for the 2023 season if he keeps it up.
Overall, Mr. Game & Watch is a character that has some really busted options, is easy to play, isn't very mentally taxing for long bracket runs (unlike, say, Peach, Zero Suit Samus, Pikachu, etc), has some really busted moves, and a good MU spread if we are to believe Miya and Maister (Miya has ZSS, Diddy Kong, Sonic, Wolf, Rosa, Hero, and Aegis in his losing tier, Maister has Ike, ZSS, and Shulk as -1. DDee also made one with ZSS, Shulk, Aegis, Sonic in -1, Cloud, Rosa, Sephiroth in Even or -1).
We're also starting to see more top players place G&W more highly lately in their tier lists recently. Many Japanese top players have thought that G&W is top 5 for a while now, and it seems many NA top players are starting to think so as well, with ESAM putting him at #3, Mr R thinks he's top 5, and probably others as well (I seem to recall there were some others that put him in top 5 but I can't find them right now, MuteAce put him in top 4 of his "win tier list" but that wasn't a traditional tier list).
Sure, G&W has some flaws. He's very light, but... He's also hard to edgeguard, has a frame 3 up-B out of shield that's really safe, fairly disjointed aerials, etc, so how easy is he to kill really? He can sometimes struggle to kill, although he does have some strong kill options. Overall, this character is amazing, and I think there's a strong case that he's a top 5 character in the current meta.