Fans who felt that One-Punch Man season 2 was unfavorably light in Saitama are likely in for more of the same in the upcoming season 3. One-Punch Man's first season was a huge anime crossover hit, attracting legions of fans seemingly overnight, and a major factor in that success was the wonderfully nonchalant main character, Saitama. A breath of fresh air compared to other anime protagonists, Saitama's combination of literally unbeatable strength and an impressively laid back attitude (to everything except buzzing insects) was an instant winner and fast became the focal point of the story.
Unfortunately, One-Punch Man's second season was released to notably less acclaim. Aside from the drop in visual quality that came from switching up animation studios, many fans felt that One-Punch Man season 2 didn't feature Saitama anywhere near as prominently as the first season. For most of the episodes, Saitama's story is the B-plot, as the Caped Baldy dons a disguise and competes in a martial arts tournament. Meanwhile, the real story is taking place outside the arena, where the Monster Association have invaded and are engaged in battle with numerous S-Class heroes across the city, with Garou still also on the loose.
Of course, Saitama does regain the spotlight towards the end of One-Punch Man season 2, taking out two big-shot villains from the Monster Association: Gouketsu and Elder Centipede. Fans might've been hoping that season 2 was a one-off vacation for the One-Punch Man, but it's likely that season 3 will feature Saitama to an even lesser extent, based on the manga series the anime is closely adapted from. The next phase of the story sees the Heroes Association mobilize against their monster counterparts and invade the villains' HQ. This leads to a series of one-on-one battles involving S-Class heroes like Zombieman, Atomic Samurai and Flashy Flash taking on some weird and wonderful creatures from the Monsters Association.
It's likely that these fights will dominate the next season of One-Punch Man, and while all the carnage is playing out, Saitama will mostly be wandering the cavernous lair alone, quickly laying out any hapless monster he chances upon. Without delving into spoilers, the sting of hero vs. monster clashes does culminate in an epic battle featuring Saitama as its star, but this probably won't occur until One-Punch Man's season 3 finale. The One-Punch Man anime may be tempted to work some additional filler segments into season 3 to give Saitama more to do, but his role in the main plot is once again set to be limited.
This is arguably one of the pitfalls of having a protagonist capable of beating foes with a single slap - Saitama needs to be removed from the action to actually allow some back-and-forth fighting to take place, and One-Punch Man uses this trope as part of its parody. However, the lack of Saitama in season 3 may not necessarily be a negative. The series is packed with fascinating and colorful characters, both on the heroic and villainous ends of the equation, and benching Saitama for a while allows more time to explore Genos, King, Fubuki, etc, all of whom are compelling and often hilarious figures in their own right. With that said, those characters aren't necessarily the ones fans tune in to see, and it turns out that being able to win any fight in one punch can be a double-edged sword when it comes to screen time.