I think a balance is good.
I worked at Target a long time ago as a Front End manager, before the days of self checkout. So I know how to cashier quickly and efficiently, and I get annoyed shopping at other places where the employees or customers are being slow.
I also appreciate just how volatile needs can be and how difficult it can be to staff. There have been books written on the subject, but in short for large stores with a lot of volume, customers do not usually trickle into checkout constantly as one might expect. Instead, they crash against the front of the store like waves. Personally when i'm shopping I try to identify these waves and time my checkout between them. At Target, we would often only have a couple of dedicated cahsiers, and would call the cart attendant or floor employees to help out for these waves. Self-checkout helps to smooth this out a lot and reduces all that walking back-and-forth.
I also hated all the upselling they made cashiers do. Target credit/debit cards and extended warranties on electronics. As an employee it was obnoxious and felt like we were annoying customers. As a customer, I was annoyed. One of my complaints about self-checkout today is how they ask you so many questions. My local grocery store self-checkout requires 5 button presses after i'm done scanning, which i think is bad design.
But also sometimes people need help. Some products are more complicated to buy. Some people are disable. Coupons are a plague upon society which machines are incapable of addressing. Some people just plain want a social experience, and it's good to have human employees standing around in general. So I like the idea of having a mix.
And, of course, Universal Basic Income so we can stop asking "but what about jobs?" about every new innovation (but fuck AI though).