Here's a sensible statement: "when appropriate, I'll punch at my opponent/partner in order to set them up for the next move (whatever that might be). However, also when appropriate, I'll strike with a decisive blow if I see an opening" (and I'm not talking about hurting a training partner).
Sounds like a good idea to me and can be applied in either aikido or karate.
That statement covers both the so called "soft" and "hard" atemi. But people tend to defend one or the other (I think the opinions are based on whether they're good at atemi or not, because there seems to be equally strong opinions on both sides).
I don't think you can judge people's degree of skill solely by their opinion on when atemi should be used. Now, if someone could careless about atemi, yeah I guess they would have poor atemi. Unless you mean that beginners (those usually with less skill) use less atemi as it may not be emphasized in their practice as of yet.
I think people based their use on atemi on a variety of factors. It could be that they want to focus on flow of the technique and want to take advantage of the momentum from the attack. It could be they are just learning a new technique and they are still confused about what the heck kotegaeshi is than when they should hit someone. But this does not mean that they don't think atemi is not important, they may be great strikers (you know 2nd dan karate but 5th kyu aikido) but leave it out intentionally to focus on another aspect of aikido.
Also sometimes we just use atemi to show uke where they are vulnerable and that they better guard their openings (my school is real big on this) while receiving their technique. In this case, atemi seems to be a training tool like a quick feint to show an opening in uke's defenses. And if you saw us doing this, it could be easily be misunderstood as poor atemi, when the purpose really wasn't to strike but to teach uke to protect themselves. (so here it's neither to disable nor to give a discisive strike; it's a training tool) Now if someone should know better, then that's another story
Now, in my opinion, where skill does come in is when you are learning a new technique. Or when the more advanced nage will give a lighter atemi, to a less advanced uke. While they are giving a "weaker" atemi and while it may appear less skilled, but in actual practice they have more skill because they are actually controlling themselves. A newer student may not be ready for a fast atemi so the older student will give a slow atemi to demonstrate where to apply it as nage.
In some cases, I have found atemi essential to technique, especially when dealing with people who are strong or like to tank. My fist suddenly coming at someone significantly stronger than me can throw them off balance just enough for me to apply a technique. Or if someone tanks, an atemi might be applied just to make them loosen up a bit. My focus in atemi is not really to disable the person. In these cases, yes, you better know how to strike. And i would think these are more kindred to decisive strikes than the distracting atemi to set up a technique.
But as a disclaimer, I am relatively new to aikido myself (1 1/2 years), and usuage of atemi is really to begin to seep in more of my practice (beginning to be more natural) as I become more skilled. So who knows what I would say a few years from now.