The thing I always enjoyed about the acting in TOS is that everyone acted larger than life instead of normal people living on a starship. Though IMO DS9 had a larger than life cast too so I give them credit for being like TOS but not copying it. That's not to say I didn't like TNG but it's acting at times was just boring. With Voyager and Enterprise. everyone just seemed one note. The Larger than life/charismatic characters are who I enjoyed watching. The more grounded to reality characters were just meh.