To some degree, perhaps. The implication that's often made about skepticism - or sometimes phrased as "Don't you need evidence that evidence is useful for determining truth?" - is that one cannot rely on skepticism or evidence, because you have the problem of an infinite regression.

— So you'd have to be skeptical of being skeptical of being skeptical of ... being skeptical of being skeptical, and so on.

This "problem" is exaggerated, mainly due to the fact that skepticism isn't a yes/no proposition. It's proportional to the claim.

If a man says he has $1, that doesn't need to be met with much skepticism. If that person says he has $1000, that'll be met with more skepticism, but we may still take the person's word for it, since it's not an extraordinary claim. By the time this person claims to have $100 Billion, that's going to require quite a bit of evidence to be convincing.

Infinite regression doesn't happen because of diminishing returns[1], in a sense. Each regression requires less skepticism. Keep in mind that atheists are practical people. They don't need absolute proof. Demonstrating something beyond a reasonable doubt is fine.

Let's say that I'm worried about saving files on my computer. I'm very skeptical about my losing my files if my computer dies. What I can do is backup my files on an external drive (or CDs/DVDs). I can be skeptical still that the backup might be destroyed too, so I can make a secondary backup. I might, still yet, be still skeptical about the safety of my files, so I might make a third backup.

After a point, I'm confident enough in how much I've addressed the concerns, to accept the end result. I'm not required to continue making backups onto an infinite number of external hard drives. I've addressed the skepticism beyond a reasonable doubt.

Most accepted science, through rigorous testing and peer review has survived hundreds of regressions. Many studies or experiments are testing prior results, confirming, and expanding on them. It's a good enough approach to be demonstrably accurate and effective in practical reality. The bottom line, is that skepticism and evidence-based investigation works.

When atheists claim to be skeptical about the existence of a God, it's because it's an outlandish and claim about something unprecedented, that not only is unsupported by evidence, but flies in the face of many things we know to be true. It's an extraordinary claim. That's why it's doubted.