Isn't 3 flags in 25 years pretty good for a 16 team comp? Blind luck would have them on 1.5ish right now. More so when you consider it includes their first few years which typically aren't times when teams win flags.
As was said above they likely closed one of their premiership windows early due to off-field drama. They have been in 4 GF right? You cant win a flag every year your team is peaking..