Well, it's subjective. A waste of time for one person could be a great source of entertainment for someone else. It all comes down to individual tastes and what you're looking for in a comic.
A villain like Shigaraki would likely be interested in the power levels in the MCU fanfiction. He's always looking for ways to increase his own power, and seeing the various powerful artifacts and abilities in the MCU might give him some ideas. He could think about how he could use similar things in his own plans to take over the MHA world.
The title itself implies that it might be a waste. Maybe it has a convoluted plot that doesn't make sense in the context of the Peanuts world. For example, if it changes the personalities of the characters too much.
Definitely not. Writing a novel allows you to express your creativity, tell a story you're passionate about, and potentially reach and touch the hearts of many readers. It can also be a form of self-discovery and personal growth.
Not at all. They can teach valuable life lessons, introduce different cultures, and improve reading skills. It's a matter of personal interest and how much you get out of them.
Definitely not. Reading fiction allows you to experience different worlds and emotions, boosts empathy, and enriches your inner life. So, it's far from a waste of time.