I suggest not to join such premium signal because it may be scam or you will not get signals at the right time . Why do you pay for it, do not take such risk. This forum is really helpful for newbie to learn more. Do your own research. If you experience u will get to know.
It is not mandatory to check the every single telegram group and join them. The more the trader fails, the more experience is gained through the failures. I don't advise joining the premium signal groups, the real traders never share their trading setups for few bucks. As you mentioned checking the recommended altcoins on the online platforms and investing these altcoins have better ROI.
I completely agree with you, it seems to me very foolish to think that someone has found a way (strategy) with which you can make good profit on the cryptocurrency and it will be scattered left and right, I think that no one would have done that whoever owns such a strategy just slowly pump money out of other least experienced traders. And premium channels are created by traders who are losers, because they cant make money on their own and earn only on those who bought access.