As DWF said, there's a big difference between being bitter, and just being an actor who's hoping to keep working for another 20 or 30 years, but is worried that typecasting from a big success might get in the way of that. It's also a pretty common thing for stars to relax about talking about their earlier big success once they hit the age when 'normal people' would be retiring anyway (and they realise that being remembered for anything after that long is still a massive achievement): forget about Who, look at Honor Blackman, Leslie Phillips, and so many more.
It probably helps that this tends to be around the point when youngsters who grew up idolizing them become prominent enough in the business to start offering them work...
How many people really remember Honor Blackman for her role in Doctor Who though? Took me a few minutes to remember she did Terror of The Vervoids.
Now if you mention Pussy Galore but she wouldn't have the role if weren't for Cathy Gale in the Avengers.
Or have I just illustrated your point?