Let's face it, this show is called Devon ke Dev Mahadev. And that title role is performed by Mohit Raina who, whether people like it or not, is the FACE of this show. Whenever this show is talked about even in media, it is he whose face is put forth. I think hence makers aren't worried much about who else is in the show.
But that said, TV industry is going on in such a manner that actors who are face of the show also get replaced (happened in case of SNS and BV and in past Ekta Kapoor even chucked out her all time popular Tulsi & Parvati!)
As viewers we don't have any choice except to watch or not. So tomorrow, even if MR is replaced, we'll have no choice but to either stick to the show or quit watching it.
I personally watch the show because it is clean and good to watch with whole family on prime time and because there's always curiosity over mythology plus the show has some good message to give always.
For a long time I used to feel MR was miscast in it. Forget MR. I wasn't happy with much of the cast except some known regulars in such shows like Pankaj Dheer, Surendra ji etc. But with time, everyone improved in acting, characters came out well and the writing of the show was surely superior. Visual quality was an added bonus.
Pooja is no great shakes as a replacement but then fact is that not even previously popular or award winning actresses can get acceptance as replacement easily! Suppose they cast Deepika Padukone in it, still people will take time to accept her or find faults with her though she's beautiful, has traditional looks and could complement MR well with her height. *This was just an example*
What's more important in case of DKDM, is that the replacement is not "totally out of place". Some leading shows brought such actors as replacement who were bad in acting and had absolutely different physicality and personality than what the character was supposed to represent! Example is there for everyone to see in a rival show in same time slot as DKDM on another channel!
In that sense, DKDM is good! I've seen real bad replacements in some of my favorite shows both in past and present. And I can say that I am relieved in case of DKDM!
I am not overjoyed seeing Pooja as Parvati, nor do I have good opinion of her from her previous shows. I don't like replacements in general. But trust me, you don't know what "bad" actually is! Pooja is okay, but it is a relief that she is not an absolute "out of place" choice.
I agree that issues with Pooja aren't just because replacements in general are hard to digest. But having seen DKDM polishing all actors that have been a part of it, I believe Pooja can improve upon the issues we have with her too. She needs only time and I think she deserves it as much as any other actor /actress who took their own sweet time to adjust in the show and make a mark on viewers.