というものではない details
Examples
it isn't simply that; that's not how it works — rejects a stated principle as too simple to act on, rather than denying a particular fact
安ければいいというものではない。長く使えるかどうかが大事だ。
yasukereba ii to iu mono de wa nai. nagaku tsukaeru ka dou ka ga daiji da.
Cheap doesn't automatically mean good — what matters is whether it lasts. neutral
謝れば済むっていうもんじゃないよ。
ayamareba sumutte iu mon ja nai yo.
You can't just apologize and call it settled. casual
経験さえ積めば誰でも一流になれるというものではありません。
keiken sae tsumeba dare demo ichiryuu ni nareru to iu mono de wa arimasen.
It is not the case that anyone becomes first-rate simply by putting in the years. formal
Formation
plain clause + というものではない（N・na-adjは だ を残す — 便利だというものではない）attaches to plain clause
Notes
the frame usually follows a ば／たら conditional and is answered by naming
what actually matters.
Related patterns
Similar
わけではない denies that a conclusion follows from what was just said (嫌いなわけではない — don't read that into it); というものではない denies a PRINCIPLE offered as a rule to act on, which is why it so regularly follows a ば／たら clause — 安ければいいというものではない rejects the rule, not an inference about one case.
とは限らない leaves the generalization standing and only admits exceptions ("not always"); というものではない rejects it as a way of deciding anything — 高いから安全とは限らない says sometimes not, 高ければ安全というものではない says that is not how safety works at all.
Lookalikes
ものではない on its own is ものだ's negative and scolds an ACTION (人の悪口を言うものではない "you shouldn't"); with という in front the target changes to a stated principle, and no one is being told off — the という is the whole difference between a reprimand and a rebuttal.
One tail apart and easy to skim past — というものだ hands down the verdict, while というものではない refuses a proposed principle wholesale (安ければいいというものではない); missing the ではない turns a rejection into an endorsement.