H.W.
First, read your contract. There likely isn't any exclusion or clause which suggests that there is a right to quit care due to the lack of a lead teacher. As long as they are within ratios (depends on your state as to what that looks like legally), you would need to expect that you have no grounds to pull your child without notice or payment for the agreed-upon period of notice.
You could, of course, say "it looks like we'll need to find another arrangement" and give the necessary notice before removing your toddler from care. You'll need to consult the contract for that. I asked parents for 30 days notice with my preschool program. It's hard to fill that child's slot in less than 30 days.
In reading your post, I noticed one essential thing missing: communication between yourself and the director. I worked in a 20-30 month toddler room for a few years and want to share a short story with you: when I started that job, it was as an assistant. The lead teacher was also fairly new. The former, very beloved, lead had *just* left that job and as it turned out, the new lead ended up having a lot of personal issues. This resulted in her being gone a lot and my holding down the fort. Although I was an assistant, I'd had a couple years previous experience with a very good lead at a different daycare and had no problem running the toddler group.
Guess what? After three weeks at this new job, the new lead was fired and I was given her job. I stayed on there for a few years, pursued more training and gained a lot of good experience. Some of us work in childcare as a career without having a degree. We self-educate, attend trainings through the county. This is not a job which pays for itself (ie-- your wage in childcare is likely not going to pay for your bachelors degree student loans, maybe your associates degree)---- childcaregivers are woefully underpaid for their work and the profession/subsidies from the government are incredibly underfunded. One of the reason that larger centers can have higher turnover is because of the burnout--- minimum wage for that job is a hard-earned dollar. (A smaller, private program will cost more, but they also usually pay their teachers much better. The preschool I subbed at over the past few years paid me $25 an hour. When I was at a center, it was just a couple dollars above minimum wage, even with experience.)
I would encourage you to keep all this in mind. Your child *does* likely receive one-on-one time from caregivers during care tasks (handwashing, diaper changes-- I always used that time to sing, chat and play with the kiddos). Diaper changes every 3 hours sounds about right. (remember that it takes nearly an HOUR to get one entire group of 8 changed) Of course, we could smell a stinky diaper pretty quickly and in my room, those were changed immediately!
So, talk with the director about your concerns. Ask what the plan is. I have to be honest, as long as the group has a daily routine, I don't know that curriculum for toddlers is going to be a make-or-break deal over the course of a month or so. Granted, I did have a curriculum, but it was very simple compared to my preschooler and, now, my homeschooling curriculum. Standard practices for toddlers are lots of adult narration as the activities happen, a variety of materials available, fun experiences (water/sand play, play outdoors daily, sensory play, stories and songs).... there's a lot more social support being provided during this age than academics. Keep in mind, the security (consistent, caring providers) and routine elements are going to be far more important to your child's well being than introduction to letters or numbers.