Speaking as someone who has just finished her first week of a CELTA course today, perhaps my perspective might be interesting?
I've been a private tutor of English (to native speakers, mostly children working for GCSEs) for ten years. I probably am finding the course easier than those with zero teaching experience, certainly, but I wouldn't say I am finding it easy, and I don't know anyone who is. Of course it's only natural that people with some previous experience at something may find training in it easier than those who don't. I dare say people with teaching experience would find an online course easier than those without it too.
Certainly, they are trying to fit a lot in to the 120 hours, but they were very clear about the fact it would be a demanding and intensive course before I signed up for it.
I don't think that it is exclusively suited to people with experience, though. The way the course is taught, and the materials provided, so far seem to really cover every aspect from the most basic upwards.
Surely it's not about what level people have when they go into the course, but what level they have when they come out of it? As long as CELTA doesn't pass people not of an acceptable standard by the end, and as long as it gives everyone signing up and paying their money over to them the required level of support and guidance so that the only thing stopping people passing becomes their own talent (because no matter how good the teaching, sometimes people just aren't suited to something) or their own commitment and willingness to work, then I don't see the issue.
Yes, CELTA seems *hard*. What's so wrong with that? Why should courses and qualifications be easy?
It seems to me another symptom of all I find worst about modern culture that people are demanding everything be "easy" and that everyone should be able to achieve everything. Not everyone can or should be a teacher - maybe I'll get to the end of the course and not be good enough, maybe I'll get to the end of the course and be good enough. But I don't think I shouldn't have to work at it!
[Oh and I chose CELTA after a fair amount of research at looking what qualifications were asked of NQTs. I don't remember seeing a single job ad that said online qualifications were acceptable; it was all a combination of experience/CELTA or Trinity Cert. I wouldn't have gone near an online course if they paid me, because it's the contact time with students offered by the face-to-face courses that I personally believe will be most valuable for me.]