Are the quick poses closer to sex - and thus "bad"? Does that make them more naked ...as opposed to marble, static nude?

Yes, our nakedness is sex-related. Not only related with health and relaxation in nature. The nakedness is even bordering on pleasure, and that's nearby to sexuality.

Unfortunately, we know about sex for sure only that it is inevitable and that it can sometimes lead to dangerous consequences.

On the other hand, it is irrational, so that - apart from reproduction - we cannot substantiate the pleasurable behaviour with arguments.

We can only try not to allow its dangerous aspects and not to rule out the demands of humanity. We can try to place it in such contexts which we guess as better.

God of some religions has sex and its pleasure as a constituent element - a subversive element in others. Because "he knows everything - but he won't tell it" we still don't know, despite many wars, which religion is right, and therefore which attitude to sex is right...

Yet, we can look at sex also as a source of livelihood for one and a source of relaxation, pleasure and fun for the other. If it does not harm anyone, it is acceptable and legal: who does not enjoy a certain form of sexually spent time, may not participate.

Ethical principles are logical and understandable, rational. But sex is irrational. Ethics is imposed onto our sexual behaviour externally. - That's why we follow our tastes, legally limited to risk-free ones. According to Kant, tastes are not to be discussed about. You can't ban someone's tastelessness - you can only allocate them to their consensual space. In fact, another person may consider as a bad taste what we like.

Of course, in practice we rely on galleries' and concerts' goers to have more refined tastes. However, there are no guarantees and no benchmarks that this is the case. Esthetics credentials cannot guarantee taste on higher plane.

Even in the art trade, marketability does not guarantee quality, often quite the opposite. The same person may have e.g. musical taste, but not visual-art one.

Sometimes we're also in the mood for popular songs that we wouldn't otherwise have listened to.

And besides all - it's also a matter of humanity to tolerate popular tastes, because without entertainment at their level, these people would be unhappy. That's why Papageno is in The Magic Flute.