That’s interesting. I could see that being true. It definitely that a issue long running shounen series run into. As from the constants power-up, those power-ups usually are distributed evenly, which results in the supporting cast struggling to remain relevant.
No kidding, Nate, and Dragon Ball Z had that major problem too once Goku and Vegeta hit Super Saiyan, and how it sometimes was too. Hell, even Piccolo got a power boost when he and Kami fused together as one to make him whole, leaving him initially the only one capable of fighting 17 and 18, as well as Cell before he began to absorb all those humans, but everyone else outside of them got screwed. Gohan still remained pretty powerful when he gained his Mystic state in the Buu Saga, plus Goten and Trunks being able to go Super Saiyan at a young age due to their dads being Super Saiyans when they were conceived as well as going Super Saiyan 3 as Gotenks, it just does leave to problems.
Naruto had that same problem going for it too, especially as it came to Kishi bring an imbalance initially in the start of Part 2/Shippuden with how Sasuke overwhelmed Naruto, Sakura, Sai, and Yamato, and yet he wasn't as strong as he seemed since he needed to wait for Orochimaru to be weak to be able to "beat" him, and even then, he nearly died against Deidara, which makes me think about if things were even really conceived in that department.
At least in some series like My Hero Academia and Demon Slayer, power-ups seem to work for everyone, and many fights can tend to not just be about the protagonists only. Even Izuku, with his recent power-ups in MHA, still can't do everything alone since he almost exhausted himself from fear and panic because he felt he had to do everything alone, which was the one weakness his predecessors sometimes had, and in Demon Slayer, when it came to fights like with the Upper Moons, Tanjiro and Nezuko also had help from either Zenitsu and Inosuke as well as a Hashira or two in addition to other friends/allies, and it came down to having to work together to be able to win.
While I like shonen series, it does get tough when it comes to not thinking out things with the rest of the cast too, which Naruto suffered from especially later on, and how I feel too it also ties to lack of development in some areas, which is one thing I want to try to really work on in my fanfic, though I haven't touched it in a bit because I got a basic idea of what I want to do, it's just putting it to Notepad that's tough, and the pandemic hasn't helped my creativity juices too much, but this was a thing even before then, especially with how sour and toxic the Naruto community as a whole can sometimes get. It isn't a lack of courage, it's just the concern of getting attacked for something like this.