Okay here's an example from film.
Watch The Lord of the Rings. Pretty cool series right? Epic, thought provoking, great fantasy with mature storytelling.
Now go watch The Hobbit trilogy and remember WB wanted it to be a PREQUEL to Rings. But it doesn't "feel" the same. It's actually really goofy in comparison. It doesn't have the same sense of weight that Rings does. At one point it's trying to be SUPER FUN! Look Legolas is bouncing from barrel to barrel in a rushing river! How delightful! At another point it's bizarrely dark as it tries to force stuff in to become more prequelish to Rings.
Another example: Disney's Hunchback of Notredame. It's a great work, that's frankly dark and beautiful and moving. Throwing crazy catholics against the Roma, genocide, injustice and more....and then there's the talking gargoyles that sing songs about pastries...? It's tone is a total MESS. They can't seem to stick with one. If you'd like a deeper look into Notredam and tone and just...deconstructing of that film and why is does and doesn't work check out the video below vvvvvvv