
I agree 100% with you. I can't count how many times I have been tricked by the high ratings in webtoons just to end up reading some shitty story about sex friends.
I remember a few years back if a mang had a rating over 9 it was an absolute masterpiece ( unique plot, stunning art ect.)
Now every webtoon, that isn't absolute trash, has ridiculously high rating.
(=・ω・=)

This is just my observation, I think most of webtoon fans here are mostly underages. Why?
1. Just like you said webtoons are fully colored, and most of them have simple storyline (of course there are exceptions like Killing Stalking, Blood Bank, etc). Sure, fully colored are more fun to read even for adults, but bright colors are scientifically proven to appeal kids than black/white colors.
2. They read here instead of buying it while a lots of webtoons here are already officially translated to English and soooo easy to buy unlike Japanese manga. They even downvoting people who only said "You can get free coins by doing xxxx, please support the author"
3. The comments section are always in mess.

I think it’s not really about age rather than their level of “experience”. In the last years a lot of people joined the “community” and found interest in manga/webtoons/anime and a lot of the new releases are those fucking webtoons. (e.g The “anime of the decade” according to Funimation is Demon Slayer. Not a bad show but definitely not the best anime of the decade. This happens to yaoi too tho.)
So refreshing to see a real manga with beautiful art and strong story lines. Funny to see such a low ratings when even the shittiest webtoon that people diss gets a 9.