No matter how promising a project might look, especially if they are new projects just look them as if they have nothing to offer and invest only what you can afford to lose. Do not keep your eggs in one basket, do not fall in love with a single coin, no matter how good they are always keep digging, many more good gems won't hurt than relying on a single gem 💍. Be smart
You have said the absolute truth but believe me many won't understand you till they learn the lesson, sadly that's how human nature is we learn beat when dealt with. Like you said already there are many coins in the market with many more still coming up, so it's wise to invest what you can afford to lose because even in most projects whitepaper they always outline the anticipated risks involved. Lastly, it's important to make wise decisions about each project before investing, in this case in terms of research etc, at least that's the best you can.