There are a lot of people who don't care about sneezing or picking their nose in public. It's so gross.
There are so many people who don't think much of sneezing or picking their nose in front of others. It's so awful.
この場合、次のような言い方ができますよ。
ーThere are a lot of people who don't care about sneezing or picking their nose in public. It's so gross.
「人前で平気でくしゃみをしたり、鼻をほじる人がたくさんいて最悪だ」
people who don't care about sneezing or picking their nose in public で「人前で平気でくしゃみをしたり鼻をほじる人」
ーThere are so many people who don't think much of sneezing or picking their nose in front of others. It's so awful.
「人前で平気でくしゃみをしたり鼻をほじる人がたくさんいて最悪だ」
people who don't think much of sneezing or picking their nose in front of others で「人前で平気でくしゃみをしたり鼻をほじる人」とも言えます。
ご参考まで!