Most of the actors know what they are getting into while signing the project and know how ITV works. Once they sign the contract, they can't do negative marketing of the show. At the end of the day, they are just the employees in the show and can't do anything about all the griviences. Also, they also know they can't keep everyone happy, so they focus on the positives and let the CVs do their jobs. It will be difficult for them to work if they keep attending to all the complaints. They are running on a really really tight schedule where they end up working 12 to 14 hours everyday.
But I have seen instances where actors are themselves not happy with the way story is going and they hint that in interviews as well. Like KSG and Wahi used to do a lot at the time of DMG. But they were really close to the CVs as well and still never used to talk completely trash about the show. Many actors leave the show when they think they can't go with how the script is getting messed up and save their fans from the torture. Like Harshad did at the time of Saubhagya. And if you see Wahi now, he has stopped working completely on the dialy soaps and works only on reality shows and web series.
For actors who are still getting a grip on the industry, they try to ignore the negative reviews publicly cause one, they really can't do anything about the story and two, they don't want to spoil their equation with the production and three, they keep the ivs on happy note so that fans don't get bored by them as well. The actors do consider the criticism they are getting, but nothing is their hands regarding the story except to do hard work on what they get or leave the show.