This isn't what flags should be used for.
Insufficient research is not a reason to flag. This is a reason to downvote.
From the help center:
Voting up a question or answer signals to the rest of the community that a post is interesting, well-researched, and useful, while voting down a post signals the opposite: that the post contains wrong information, is poorly researched, or fails to communicate information.
Flagging is for serious problems only, that will often result in the removal of the post from the site. Reasons include:
- is spam
- is abuse of the site
- is rude
- is plagiarism (this requires a custom moderator flag)
For questions, there is:
- unclear what you're asking
- too broad
- primarily opinion based
- off topic
In these cases, the question is closed, not outright deleted, although it may get deleted later on.
And for answers there is
This is not a complete list, but I think it serves to show that flagging is for serious problems only. If something is low quality - and poor research falls under this - then downvote it. Don't flag it. As a moderator (on Literature.SE), I can tell you that there's a specific decline reason for this:
flags should not be used to indicate technical inaccuracies, or an altogether wrong answer
And much the same applies to questions - that they shouldn't be flagged for 'technical inaccuracies' or whatever.
Flagging is a tool to remove content from the site. If something is explicitly against the SE rules, it will get closed or deleted. On almost every Stack Exchange site, 'Insufficient research' is not a reason to close.
There is one exception - that's English Language & Usage. They have a custom close reason to close questions that aren't sufficiently researched. But that's something that one site has agreed on, and can't be applied to the rest of the network. If you'd like to consider closing low research questions, then I encourage you to write a meta post explaining how they are harmful for this site and why you think that they should be close worthy.
Essentially - flags are the way the community says there's a significant problem with this; it should be closed or deleted in ways that are determined by Stack Exchange and the individual community. Poorly researched questions don't fall under this here (yet?).