というものではない is an expression in Japanese that indicates that ‘there is no guarantee that (A)’, or that it is ‘not necessarily (A)’. As this structure is just a combination of と, the う-Verb 言（い）う ‘to say’, もの ‘thing’, and ではない ‘isn’t’, the literal meaning can be thought of as being similar to ‘it’s not a thing that one can say is (A)’.
は may be replaced with も, with only a slight change in nuance. As with many grammar patterns, the version with も will be considered a bit more emphasized.
というものではない may follow any word in its standard form, but may occasionally be preceded by だ when used with nouns or な-Adjectives (despite not being required).
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いい大学（だいがく）を出（で）たからと言（い）って、いい会社（かいしゃ）に入社（にゅうしゃ）できると言（い）うものではない。
There is no guarantee that you will get into a good company just because you graduated from a good university.
洋服（ようふく）は高（たか）ければいいと言（い）うものでもない。
It is not necessarily true that clothes are better if they are expensive.
アプリの機能（きのう）は多（おお）ければ多（おお）いほど便利（べんり）だと言（い）うものでもない。
The more features the better is not necessarily true when it comes to apps.
あのブランドが人気（にんき）だからと言（い）って、あのブランドの商品（しょうひん）がいいものだと言（い）うものでもない。
There is no guarantee that that brand’s products are good just because they are popular.
In most cases, this grammar pattern will indicate that while most of the time (A) might be something that is expected to be true, there are exceptions.
Fun-fact - Although not specifically limited to it,
というものではない sentences are often preceded by phrase including であれば. These sentences merely emphasize the fact that ‘even if it’s (A), it doesn’t necessarily mean that (B)’.
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日本語（にほんご）が上手（じょうず）であれば日本語（にほんご）の勉強（べんきょう）をし続（つづ）けなくてもいいと言（い）うものではない。
It is not necessarily true that you should stop studying Japanese, just because you are good at it.
プレゼントは高級（こうがく）であればいいと言（い）うものではない。
It is not necessarily true that a gift is better the more expensive they are.