When I was still a newbie, I ran into this issue a lot for mostly three reasons: buying crappy cigars, not letting my cigars rest and spending WAY TOO long thinking that 70RH was preferable.

After a lot of trial and error, I now only find myself having to pitch a cigar maybe once or twice a year. Over the years, I've come to figure out which "budget" cigars are actually worth a damn and which are dog turds--and I pretty religiously stick to known commodities. I also let all my internet purchases rest for a minimum of three months, no exceptions. I've wasted too many cigars by smoking them ROTT.

If you stick to quality cigar brands and let them rest adequately, you really shouldn't have issues with "bitter" cigars. And no, they won't get any better as you smoke them. The reason cigars need so long to acclimate is because the humidity needs to make its way down the open foot to the closed cap. I've smoked cigars that I have rested for only a month and they've turned acrid at the halfway point--because they're halfway acclimated. Patience is rewarded in this hobby.