Like, I expected way more effort than what I have received from them.

yeah, i'm a college student and i'm shocked quite frequently at how little effort some people put in when in group projects or when handing in papers. at the same time, a lot of it is because they have no clue how to do stuff properly and are too afraid to ask. i was never taught how to write academic papers before college so when they were first assigned to me i had to put a decent amount of work in. lots of people handed in pretty bad papers but i don't fault them because if it's your first semester you should probably be given more help and guiding.

but as other comments have pointed out, saying "i want more effort" isn't good advice or criticism. they aren't playing sports, they are doing academic work. you should focus on what they should improve rather than say "do better". so if their writing is bad say that and give them some pointers. if they don't know an important part of their course say that and try to point them to material that discusses that topic.

i know that you probably have a ton of students and it might not be feasible to do this for every single students, but i can assure you that if you do it for some they'd probably be very grateful. this is stuff that only takes a few minutes but means a lot to people.