How reliable is copy trading? My dad started doing it and has earned approx 16% since November 2018. Seems a little too good to be true.

It's only as reliable as the person you are copying from. So if the trader or the 'copying' platform decides to pull the plug guess what happens. While 16% returns is decent at 5+% a month since November, don't forget this may vanish at any time without warning. Profits and account may also vanish anytime especially if the platform the funds are parked under is not regulated here.

I'd suggest getting your dad to pick up the instrument he's copying trades on by his own. This way he creates a system which he can deploy at any time.