The post office is not

doing the job it is supposed to be doing.
I ordered something from the UK in early March. The company in question dispatched it very promptly and let me know it was on the way. It didn't come...and it didn't come.
Once before a parcel from the same company was delivered to the wrong address and sent back with a "not wanted" on it. I spoke to the Post Office about that. They were full of apologies but said, "there is nothing we can do". 
Nothing they can do? I thought it was their job to deliver parcels to the correct address? (And yes, the address on the parcel was correct.) 
In between two books have gone missing. Nobody seems to have been able to track those down. The are not new books just copies of a long out of print gardening book the Senior Cat wants to give to other people.
A letter sent from a neighbouring state took seventeen days to get here. One posted from the other side of the city took eleven days.
A letter sent to the UK took almost three weeks to arrive and another sent over three weeks ago has not yet arrived. Why?
A very good friend in the US has sent some knitting literature for a group of young people with disabilities. We are both very fond of these young people. I have not told them anything is coming as they would be upset for her that the envelopes have not yet arrived. 
And this last parcel I was expecting did not arrive. I informed the company and we both gave it a little more time. They then offered to send it again - or get a refund.
Something made me say "get a refund". Things are too difficult right now and I had sourced a substitute elsewhere anyway. Then, this last week, the parcel arrived. It had taken eleven weeks and three days to get here. Why?
The company in question has already given me a refund. I have emailed them and informed them that the parcel has arrived and asked them to bill me again so I can pay them. It is annoying and time consuming for them and for me. I have also spent money on a substitute which is not quite as satisfactory.
I know there is apparently an increased volume of parcels in the post right now. I also know that extra precautions are being taken because of the Covid19 situation. The increased volume won't last but it does not account for something sent in early March - before all the additional security measures were put in place.
The volume of letters has apparently dropped so much that deliveries no longer take place every day. Why does it then take so long for a letter to get somewhere? Even allowing for all the measures being taken to ensure staff are safe (and so they should be) the snail like speed of mail is alarming. 
There are important letters not being delivered in a reasonable length of time. The Post Office is simply not recognising that not everyone has access to email and others do not have access while the library computer service is closed. 
I am annoyed about the parcel but I know there are much more urgent letters not being delivered in a reasonable length of time. The CEO of the Post Office is paid a massive amount - perhaps it is time to use some of that on extra postal workers?