Due to lots of scams and frauds then its never been recommendable for you to join up those paid groups.Unless if they were free then you could really join up if you wanted to.
Even for free, most of those groups has something for you to take even they don't charge you. And that's your participation to the ads that they might send to their members.
If you think that you're okay with that and that's the benefit that they can only get you in return of earning some good rewards from their signals, it's up to you if you're totally okay with that exchange.
I've got a point about your saying as trust is very important here. It was okay earning a few bucks from trading and following this signal group but I'm not sure how greedy people will think about it as for sure they wanted more and more. These signal groups are certainly looking for greedy people as they can easily manipulate their minds and likely, they are too easy to scam.
It was not wrong to use this platform but because of many negative feedbacks and reviews about these groups, it actually creates worries and not advisable to join with.