Hi. I have completed my MS lab work recently and am looking for a full time job. I want to get some practical experience and save some money before starting my PhD. I've been offered a job as a lab demonstrator which has the requirement of a BS degree. I feel like I've wasted 2 years of my life doing this MS and I should have gotten this job 2 years ago. Lab demonstrator and helping with bachelor programs is great when you're doing it part time with a PhD but I'll be doing it full time and that's what'll show up on my CV from Nov 2018 to xyz.

I would greatly appreciate any advice.

A BSc is the minimum qualification needed to do the job. I don't know much about your field but I doubt the employers expected to give the job to someone who only had a BSc unless that person was a really strong candidate at interview. In my field a lot of job ads state that the minimum requirement is a teaching diploma but most jobs go to people with master's degrees and those people don't feel that they have taken a job which is beneath them. At least you'll be working in an academic environment with opportunities for networking and a chance to get a bit of teaching experience. I would make the most of it.

Take the job. Look for a better job whilst enjoying the privilege of being able to pay your bills.
There are plenty of graduates working in call centres and no end of people with PhDs working as lab technicians.
Think yourself fortunate to have found a technical job at all and stop complaining. You seem to have a bit of an attitude problem and an entitlement complex. You should drop that ASAP.