The game letting you do it is a very poor excuse
I wasn;t excusing it. I was saying if it were NOT an exploit, you would not be able to EXPLOIT it, by defniition. So if you can't do it, it isn't an exploit, if you can, it might be. If it's not within the game (which means you cannot go back to the game interface and relog, for example, since that is outside the game, not in it), then it is also an exploit.
But "exploit" is a fairly meaningless word if you just ask as vaguely as the OP did. Logging out so I can take a pee is an exploit. I don't risk losing my ship whlst busy doing "real life" things like urination. However since this is a game and NOT an actual pilot situation, going offline and shutting it all down is not seen as exploiting to my uneven benefit.
So, like I said, the better question is whether some specific thing should be done by any form of exploit.
At no pont did I say it was fine to play an exploit "because the game lets you". The game lets me log off to pee. And that is fine. Exploiting the game interface, but nobody cares, and "the game lets you" is 100% valid. the game lets you pull the cord out of the wall (can't stop you in fact), and if that happens because someone pulled the wrong plug out, this is not an exploit. If I do it because I wanted to grief someone but they turned the tables, almost everyone agrees that this is NOT fine.
Depends on what the exploit is and WHY you do it.
Doing it to get the right mission rewards for a G5 mat indicates a problem somewhere else.
Eiiher the one demanding G5 mats faster than "they need" or if that need is valid to some degree, then the need should be filled by a non exploit method. E.g. making them rewards for CQC.
After all high level engineering is mostly a requirement to PvP, and that's what CQC is for, so it fits the need.
Exploits are allowed by the game. Full stop. It's not the allowing by game that makes one exploit fine when another isn't. It's why it happened. How it happened. Not what happened so much.