it is not that
it doesn’t mean that
it is not always the case
Structure
- Verb + というわけではない
- Noun + というわけでない
- いAdj + というわけではない
- なAdj + だ + というわけでない
[Used to deny that something mentioned earlier is not a reason for something・to state uncertainty about something・to state that something is not always the case]
@mrnoone I’m hoping you can help with some confusion I have on this. Usually nouns and na-adjectives follow the same grammar pattern, but here nouns don’t include だ where the na-adjectives do. However, some sentences seem to handle this inconsistently and still put だ after the noun. Can you explain this? For example:
全てのキノコが毒菌だというわけではない。
Hey 
The answer is simple, the だ is optional. You can include it or not. Both ways are correct.
Hope it helps 
苦情というわけではなく、提案です。
@mrnoone Is there a reason I can’t say じゃなくて or any other variation of that as an answer?
Hey!
All forms are correct:
苦情というわけではなく、提案です。＝ sounds like written document/ very formal speech
苦情というわけではなくて、提案です。＝polite speech
苦情というわけじゃなく、提案です。= friendly (くだけた) speech
(if we are speaking about じゃなくて and the like) then those are correct (without any context), but it would mean a slightly different thing. (in this case, there is no context, but there is a hint, though ultimately we want to add context in every sentence that needs it, especially in this case. Sorry for the inconvenience 
)
じゃなくて is much more assertive than わけではない (which can be used to say that something is not 100% certain.)
Also, わけ means “reason”. So it basically means, “it is not the reason (your claim) for” something (what I did). It is used when rebutting someone’s claim.
context, parents try to feed you something you don’t like: 好きじゃない I don’t like it
context, you buy natto at store (because someone asked you to do that), and friend you are shopping with asks you “whoa, didn’t know you like natto” (he assumed that you liked it): 好きなわけではない It is not like I like it
I hope it makes it more clear now,
Cheers!
The hint wasn’t available when I answered (since I have it hidden by default) and it marked me wrong right away instead of showing the hint.
Made it so that it will show hint from now on!
I will add context to every sentence in this grammar point within this week!. It should solve the problem in the best way.
Sorry for the inconvenience and thank you for the feedback!
PS
If you find grammar points that really need context, just PM!
Can someone help explain the differences with these? In my head, they’re all “it doesn’t mean that ~” but I often get marked wrong without a nudge.
わけではない
というわけではない
ことにはならない
ということにはならない
Seconding (and bumping) this question 
@Melanthe @FredKore
Those two are very similar expressions.
There is a strong tendency to use ことにはならない with ても and からといって(からって). As in:
AからといってBことにはならない
A[ても]Bことにはならない
It is fairly uncommon to use it without those two constructions in the preceding clause (part of sentence). It is also more often used in refuting general statements. So it is a more limited expression, but basically interchangeable with (という)わけではない.
わけではない can be used with からと言って and 「ても」 but it is not a requirement and it is quite common without those. わけではない is generally used when refuting/disagreeing with a statement of the interlocutor (a person we are talking with). It can be also used when refuting general statements and as a very indirect way of refusing. So it has more use-cases. But I would say it is also generally interchangeable with ことにはならない.
When it comes to という, it is generally used when なadjective or noun directly precedes わけではない, so instead of
Noun/na Adj + な + わけではない (some even consider this unnatural)
Japanese prefer to use Noun/na Adj + というわけではない.
It is also common in AからBというわけではない construction (instead of using simply わけではない). With verbs and いadjectives you can use both without any special nuances.
I hope it helps,
Cheers
PS
It’s my personal opinion, but わけではない is “stronger” expression.