Animation is a medium not a genre.
There seems to be a great misconception in America regarding animation. Assuming you've read the title of this article you probably know what it is. Over the last century animation has come to be pigeonholed into a couple of categories with little to no wiggle room. That's a problem.
There are two categories of mainstream Western animation. The first is children's entertainment. If you head to your local multiplex with the intention of watching an animated film generally you only have a couple of kid friendly options from DIsney, Dreamworks, or one of the other studios trying to capitalize on the kid demographic. 
This wasn't always the case. There was a time when animation was considered an art form. When Snow White premiered at the Carthay Circle Theatre it recieved a standing ovation. It was hailed as beautiful and life changing. They made it a custom Academy Award made of one regular sized award and seven dwarf sized awards. So what happened? Why does the average American think of animated movies as worthless kiddie fare?
This can be traced back to the 1930s. In the 1930s the MPAA (at the time the MPPDA) instituted the Motion Picture Production Code also known as the Hays' Code. This code was a set of moral guidelines adopted by major studios limiting the use of profanity, sexual content, violence, and other things deemed morally unfit to be put to film. Animation was no exception to these limitations. Studios such as Disney and MGM (Hanna-Barbera) adapted to these codes by creating squeaky clean characters fit for the whole family. Others studios like Fleischer Studios (Betty-Boop, Popeye) tried to censor their existing characters to fit these new guidelines only to go defunct.
However by the time the restrictions were lifted in the late 60s going into the 70s the damage was already done. Animation had established itself on its family friendly characters. Why would Disney risk making darker animated works when it could consistently make money on adapting family friendly versions of fairy tales? While live action films entered the dark, gritty, experimental phase of the 1970s, animation remained stagnant.
Since then a couple animators have made attempts to bring animation back to wider audiences with little success. Ralph Bakshi probably had the most success in that field. He created the first X-rated animated film "Fritz the Cat." While that film was a massive hit grossing 90 million dollars on an 850 thousand dollar budget that quickly proved to be an exception rather than the rule. After that he's most notable for his adaptation of Lord of the Rings and the massive flop that ended his movie making career "Coolworld." 
Other than Bakshi the only animator worth mentioning is Don Bluth and the movie that ended his film making career "Titan A.E.". In the 80s and 90s only one animator consistently stood toe to toe with animation giant Disney and that was Don Bluth. With such hits as "An American Tail," "Secret of Nimh," "Anastasia," and "The Land Before Time" Don Bluth proved that other studios could make a place for themselves in the animation medium. However Don Bluth also dashed any hopes of animation stepping outside of the child friendly mold with his film "Titan A.E.". "Titan A.E." was Don Bluth's attempt to make an animated sci-fi epic. Unfortunately "Titan A.E." failed to make back its massive 75 million dollar budget, only making 37 million dollars at the box office. Simultaneously ending Don Bluth's animation career as a well as any future attempts for studios to step outside the usual animation wheelhouse.
Of course all it takes is one massive hit to change people's view. Which brings me to the other category of mainstream Western animation, television comedies. In 1987 the Tracy Ullman Show introduced an animated segment satirizing the average working class American family. That segment was called "The Simpsons." A couple years later "The Simpsons" became so popular that they got their own half hour sitcom. What happened then changed the perception of animation going forward. "The Simpsons" became huge. The characters, the catchphrases, the voices all became part of the American lexicon. There was praise and awards. They got their own star on the walk of fame. Most importantly though they spawned a slew of other animated comedies skewed at adults and those were also successful. Shows like "South Park" and "King of the Hill" proved that "The Simpsons" wasn't a fluke. Now animated comedies are as varied and watched as their live action counterparts.
Despite "The Simpsons" and all those other shows, animation is still a fringe form of entertainment. Anime has offered an alternative for people who want different forms of animation. Though while anime does offer animation in other genres like action, drama, or romance typically they are too steeped in Japanese culture or tropes to connect with an American audience. If it was going to break into the mainstream it probably would have done so when Dragon Ball hit it big.
2018 is an important point for the future of animation. As the industry is making the transition from traditional film and television experiences to the future of streaming. A couple of streaming services are dipping their toes in the animation pool. Hulu is doubling down on traditional anime offering a large quantity of anime from a variety of studios. More intriguingly is Netflix who is funding and producing their own animated content in the form of shows like Castlevania. If these shows prove popular it's possible for another Simpsons style paradigm shift and perhaps animation could prove to be the valid medium it once promised to be.
But why should you care? Animation is a medium unlike any other. It can take you to worlds and places that can't exist anywhere else. Frankly I think people like animation more than they readily admit. Look at Avatar, the highest grossing film ever released. 90 percent of that movie was computer animated, but since there were some live action elements it's treated as a live action film. If people were willing to forgo those live action moments and let themselves get absorbed by the animation they could find something beautiful. An art style, a fantasy world, or something you've never thought of before. So if you find yourself writing off a show or film just because it's animated, give it a chance. Remember animation is a medium not a genre.