1. You need to sincerely and without bias, study the project whitepaper. A scam project will always use ambiguous words and big grammars to confuse their readers. They would use words like "Blockchain, DeFi, Technology, Node, Proof of Work (PoW), Proof of Stake (PoS) etc. With this they make their readers especially those new to the space to assume that they are well informed about the ecosystem thereby buying their trust with ease.
A good project would outline the core use cases of their token clearly stated on their whitepaper.
Studying the whitepaper is always a top priority when it comes to investing into new projects.
On the other hand though, I've seen numerous projects with very good whitepaper and it looks interesting but ending up as a scam so...whitepaper can also be a basis but just be vigilant still.
2. You should check whether the identity of the team members are known. Most scam projects do not reveal their identities so that they won't be easily traced. Most of them use false or fake names and social links to further buy the trust of their investors.
This might be the case back in the days where ICO's are still popular but right now, there are some projects who are successful at least but the team members are still anonymous.
After all, developers being anonymous are still a red flag for me because anytime they can run away with the investor's money without any trace whatsoever.
3. Their telegram group and channel are usually very full but with few real members and more of bots. This makes users who does not know the difference to assume that the project has attracted many persons.
Telegram? Its full of scams and bots like you said and I don't like the platform as well.
Overall, what you all said was true but in the end you will not know which projects are scam and which are not. There is a famous quote saying that a project can't be called a scam until it turns out to be one. As long as there are developments, communications from the dev etc. it will still not be a scam even though everybody is saying that it is.