If it's really dapp, then it means the source code is available on the blockchain (which anyone can access easily) and anyone can read/audit the code to make sure whether the dapp is scam, buggy or work as expected.
But if you don't have such knowledge, then all you can do are :
1. Check review/comment from people who've used the dapp
2. Check whether someone have review/audit the code and it's result
3. Use website such as
https://dappradar.com/ which usually only list proper/not scam dapp
The fact is that many comments naturally approving any application can be paid by the fraudster or made by him from different accounts. This is a very common practice. Unfortunately, many users do not know
https://dappradar.com/ and this site may not include some of the new Scam apps on its list,as far as I understand the rating is formed from reviews.
Checking out dappradar you can really say that there might be some scam apps being listed but the question why would you go into the last ranking if theres top one? Big chances or those who are on top would be
legit ones if you do based on user and volume of ETH involved.
Right on point. Usually, the top ones are the legit ones.
But, still you need to do your own due diligence.
Reviews/comments are just your guide to dig more about the project.
You really can't tell if those ratings are really valid. Who made those reviews, where those ratings come from?
It's hard to trust those ratings because in reality sometimes, their performance is the opposite.
So, read and do your research regarding the project, if you really want to invest.