Recently I saw some of my favorite works made into animations and movies. Those are usually good news, except that sometimes the IPs are only used as cash cows to capitalize on the existing fans, not caring about preserving the charm of the original franchise.
As I perceive it, media mix brings attention from a much different audience. A successful one can create new fans, with the caveat of a more diverse target audience and thus making subsequent works and marketing harder. Some stories even go out of control from the original creators, either due to the publishers manipulating or trying to please the audience in the wrong way.
Media mix also fails in several ways. Failing to catch eyes or regressing from the original IP are the common problems. But in the latter case, the result might still be praised upon newcomers while gather criticism from the original fans. This situation can become more vicious as the work becomes difficult to move on, due to having multiple pools of core fans with possibly conflicting takes on the franchise.
In the end it all comes to capitalism. If a series shows profitability, there is no choice other than pushing it to an even wider audience. Gaining a "cult following" often means a commercial failure, and creators of these works will struggle to make a living, but I really like when the number of audience do not decide the artistic process. An artist I know is a proponent of basic income, as a solution to this problem, and I think it is a fair argument.