Hi Caroline,
Unfortunately, there are guys on dating sites who are just there for an ego boost or will only put in real effort with someone they find to be the most attractive. Try not to take their lack of effort in conversation personally.
If anything, this should teach you that simply matching with someone that appears to have a lot in common with you on paper, doesn’t guarantee that you will both engage in robust conversation.
Once you notice that they aren’t really participating wholeheartedly in conversation, stop putting out the effort to keep it going. Only focus your attention on guys who are showing a true effort in conversation.
Oftentimes, you will know who these guys are by how often they ask you questions and how substantive those questions are.