“Not infallible” doesn’t mean “subject to change at a Pope’s whim (or some guy on the internet’s supposition about the Pope’s whim)”. The reason why non-infallible teachings are reliable is because it is very unlikely that they will be changed.
Certainly, it is not licit for a Catholic to dissent from such a teaching simply because of the possibility that a future Pope might overturn it.
“Nor must it be thought that what is expounded in Encyclical Letters does not of itself demand consent, since in writing such Letters the Popes do not exercise the supreme power of their Teaching Authority. For these matters are taught with the ordinary teaching authority, of which it is true to say: “He who heareth you, heareth me”; and generally what is expounded and inculcated in Encyclical Letters already for other reasons appertains to Catholic doctrine.” - Humani Generis #20