For a start, I've never been rude or shouty to anyone, I've enough self control to remain polite and friendly but I'll be assertive if necessary, without aggression or insulting behaviour, etc. Being assertive is not the same as being rude, aggressive or insulting! I can insist on my consumer rights being honoured with a smile, a please and a thank you. Shouting and insults gets you nowhere. In fact, I'm sure some receptionists, shop workers, etc hate it when I remain polite, calm and smiley as they can't pull the "we won't tolerate abuse to staff" card to fob you off and force you to leave!
But, by God, it's hard to stay polite and respectful, when you're on your 19th phone call totalling several hours in total (as per telephone itemised billing) to the car insurance company after an accident caused by someone else, and you've had a succession of calls answered by people who are completely disinterested, playing with their children or their dog, watching TV or breaking the call to answer their front door, and as a result of that, not actually doing their job! That's not down to staff shortages, it's down to staff not actually doing what they're paid for. Yes, it's the company's fault for not properly managing their WFH staff, but also the employee for not actually "working" their working hours!
Back to the purpose of this post, I'm not sure it's Covid itself that's been the problem, but it's the side effects of covid, i.e. the epidemic of people working from home, staff/product shortages, automated processes to reduce human contact that haven't reverted back to pre-covid, "because covid" becoming the easy and lazy answer to poor service, etc.