Where did this meme come from that Cuphead doesn't have good gameplay? I always hear a lot of people say the graphics/animation/sound presentation "makes up" for the gameplay.
As someone who has literally played almost every run and gun in existence, Cuphead's gameplay is absolutely top notch. The boss challenge and variety, the huge amount of unique attacks and environmental hazards (and how they are relevant to the theme of the boss) and how they all combine together in semi-randomized patterns, the controls, the multiple forms/stages of a boss with dynamic progression, the many unique weapons that are all good in some capacity and each have their own strengths and weakness, the charm system, the excellent animations with an extremely tight hitbox, the parry sytem, expert mode that completely shakes up the boss fights. It's all just so incredibly well done. It absolutely BTFOs basically any run and gun game in existence out of the water in terms of boss fights, and it has much more and longer (without being bullet spongy) fights than these games too.
Even a great game like Contra Hard Corps has way more shallow, static, and predictable bosses. Something like Gunstar Heroes has way simpler and cheaper bosses as well as horribly shitty controls, an ugly artstyle, and higher difficulties just makes bosses massive sponges. Alien Soldier has absolutely pisspoor controls and horrible boss balance. The only run and gun with boss design even close is the Metal Slug games, and even many of the best bosses in those games are about on-par with the average Cuphead boss.