Personally I’ve been following 2 signals for over a year now and am happy with the results. Not crazy returns but fairly reliable overall (good months and bad months). I think while learning to trade it can be very useful to follow or watch other traders. You can see first hand the things which you may have read about in forums e.g. stick with a winning strartegy and being prepared to trade through periods of drawdown while still trusting that previously winning strategy.
As for not being able to trust people selling signals - why not? If someone has a reliable system they might not be making mllions from it as they don’t neccessarily have spectacular returns, just reliable, consistent returns (e.g. the signals I follow make around 3% per month low to medium drawdown).