Pretty much inevitable as one increases vaccine accessibility given that once the vials are punctured they'll go to waste within the day. Walk-ins without appointments are great for getting marginal vaccination up, but not so great for keeping wastage in check, particularly when the remaining pool of people interested in getting vaccinated slows to a trickle.
Wastage for non-coronavirus vaccines can be extremely high upwards of 50% or more in developing countries, but few vaccines are as precious as the coronavirus vaccine.
I do get a little angry at people lying about immunocompromised status to get third boosters, but this wastage is even worse.
I wish the vaccine hesitant considered this wastage more. While the US waits for them to make up their mind doses are spoiling that could go to other countries that want more doses.