Customer service standards have been nose diving for years. Long before Covid, but yes, that's made it worse.
I've no doubt that some customers are rude/entitled, etc., but the majority really aren't. Yet, far too many customer facing staff are rude, unhelpful and generally unpleasant to ALL customers, whether they've been rude or polite.
The lack of customer service is what is causing more and more, usually mild mannered, customers, to be more assertive etc.
Ask a perfectly sensible/reasonable question in a shop or on public transport, and (assuming they don't completely ignore you), you'll get a grunt or a nod or a shake of head, with virtually nothing verbal, and no help whatsoever.
My OH is the most mild mannered man you could find, never raises his voice, never aggressive, yet our local hospital has driven him mad due to their incompetence, shoddiness, general "can't be arsed" attitude, etc., and he's having ongoing cancer treatment. I've accompanied him to appointments and during treatments, and the staff really couldn't give a toss - and no, they're not "too busy" at all, they've just got some kind of "attitude" that means they do the bare minimum and just spend most of the time whingeing to each other!
Same at our local post office. The young lad who staffs the counter barely ever speaks, no pleasantries, no "good morning", no "thank you", just grunts the price and has a general attitude that customers are interfering with his mobile phone watching. It's not surprise that some customers get annoyed with him when they ask for advise or ask questions and he just grunts back, usually telling them to check online! That's really helpful!