Would it be possible to use an NFC tag with android to launch an Alexa routine?
Yes. You'll need to expose a virtual contact or motion sensor to Alexa and use that as the trigger for your routine, then you'll need a rule on the Hubitat side to make that sensor go momentarily active ormopen when the NFC tag is scanned. A local or cloud endpoint trigger for a Rules Machine rule (depending on your needs) would be an easy way to make that happen, then you'll just need a mechanism on Android to hit that endpoint when the tag is scanned (Tasker or some other go-bwtween; I'd avoid hard-coding the URL into the tag, especially if the automation needs any reasonable kind of security).
Ana yeah, there might be a way to leave Hubitat out of it entirely...I don't use Alexa for automations much.
With tasker on your phone I believe you could do this. Possibly without involving hubitat at all. (not sure if there are tasker plugin to launch alexa routine).
I got it going with a combination of Tasker, auto voice and trigger. I can read an nfc with my google phone and run a routine on an Alexa device. You were right I could leave the habitat out of it entirely.