Easy to say, hard to do.
Besides: That isnt actually useful to the artist, and most artists seem to realize this eventually.
After all, how can you find areas where you need to improve if the people who look at your art wont tell you what they are? One of the most irritating parts of creating something is that you, the creator, are TOO CLOSE to it. You cannot spot certain issues because of that. Critique is very important in the process of improving one's skill. With some things, a LACK of critique can outright harm the final product. In my wacky game-development exploits, the final product came out as good as it did BECAUSE of people pointing out flaws without hesitation during testing. It would have been nowhere near as good if they kept telling me and the rest of the team that it was all good simply because that's more "supportive".
Frankly, I always consider it outright disrespectful to lie to someone by saying their work is somehow perfect with no flaws. That doesnt ACTUALLY support them whatsoever, because it cant help them with their REAL goal: getting better at what they do, so they can make true masterpieces eventually. It could instead outright slow them down!
If I see a problem... you bet I'm going to point it out... and if the person in question cant handle that? Well then, we've found a whole other type of flaw that MUST be ironed out if they want to reach a truly high skill level.
Of course, this is assuming that I understand the subject matter enough to do so. You'd never see me pointing out the flaws in, say, an ice skating routine, as I have no bloody clue what's going on there. Well, I guess if the skater outright ran into a wall, I could point that out.
And yes, I did in fact spot the bit in @Lili G 's original post where the friend was showing art that they found, not that they made... but I'm just pointing this out in a general way, as it is quite important if you're dealing with the person who actually made the thing in question.
Just my thoughts on it as someone who does this pretty much constantly. I tend to be a lot more harsh and spiky about it though. I call myself "Misery" for a reason.
It depends on intention. If, for example, you were to show your art to your parents, you are likely not seeking an art critique. You're seeking appreciation. No one would ever use the word "perfection," that's not relevant. It's a loved one celebrating your work with them.
If a person goes to another artist seeking critique, that's when comments are appropriate. I don't remember exactly what has been said in this thread, but is the OP an art critic or at least an artist? What credibility do these criticisms have? If they're pointing out a crooked line, that's just rude. Crooked lines are obvious. That's not helpful.