It's still the case but the ESTA is not valid for work which you could argue they are doing.
ESTA’s are valid for work or pleasure purposes up to a maximum of 30 days at a time I believe. And as has been pointed out, all you need is passport information and it’s pretty simple to do. Not a grand conspiracy as some people seem to think, as always, with this show.
I suspect you might be pushing it to go in on an ESTA for X Factor as a contestant. May depend on how the talent are contracted. If they are paid for their performances then they may be out of scope for Visa Waiver / ESTA. I'm not an expert - but crew would need to be on something like an O-Visa - and it's possible talent might need to be either O or P (suspect more likely to be O)
Reading up on this, I suppose it depends on whether the authorities view such work as 'journalism/media'.
The contestants are not being paid locally in the US, so it's not a case of US employment. Everyone I know
attends the NAB show in Las Vegas on ESTAs, because in effect it's nothing more than a massive business meeting. Mind you, always put 'Electronics Engineer' rather than 'Broadcast Engineer' as occupation
(Same applies for UK car insurance applications)
However, I do agree, best these days with the US to err fully on the side of caution !