Since they did away with a dedicated fitting room attendant, I really don't have the time or inclination to worry too much about theft. If I happen to notice a sketchy person going in, or a group, I will hang around a bit to let them know someone is watching, and wait for them to come out. It's honestly more so I can keep up with the go-backs and maybe guilt them into bringing out their merch instead of leaving it all over the floor in a stall, but it also works to deter a bit of theft.
If I find something other than loose tags, like empty electronics packages, I will alert AP. But I'm not getting worked up over it - if the company doesn't think the fitting rooms need monitoring, then so be it.