I don't think it was so much about getting Shirley in the Vic - she is being taken out of that dynamic now, isn't she? She will be bought out soon enough and they have already taken her name down.
But, and I say this as someone who is a fan of Shirley, I would rather she wasn't connected to the core four. I liked Shirley and Mick and I liked the Mick/Shirley parentage story but with everything else going on, it has got swept under the carpet and it could still have been done but with her brother coming in with Tina and not being connected to Linda/Mick/Lee/Nancy in the Vic.
I don't think Shirley has hindered their potential though - I think the rape and repetitive nature of their scenes is what has hindered them, as well as Linda and Mick being at the forefront of the show and the forefront of every advert or promo for the show. Generally I find the core four quite boring as characters - I feel like Linda is just a mash up of past landladies and doesn't really have an identity of her own, Mick - I mainly see as Danny Dyer and Lee is dull and forgettable. Nancy does show promise though. I don't see the chemistry between Mick and Linda as a couple and don't like them in the Vic either.
The likes of Babe, Tina, Shirley, Sylvie, Stan and Buster are flawed characters but are much more interesting and watchable to me. (If we forgive the terrible rape story). I see them as a separate unit to the Vic Carters now anyway.