"Well at least you know that employees have to agree to be furloughed"
If your employer tells you that you are being furloughed, you can't exactly refuse. If you worked in the hospitality sector such as restaurants, inessential shops, or tourism, there was no work to do anyway and no way you could refuse to be furloughed.
Even if you don't work in those sectors directly, the closures created a domino effect and affected income for businesses across many sectors.
"A lot of businesses didn't have to close, or at least, they chose to close even though they were allowed to stay open. Why should everyone else pay for that?"
Some businesses were not specifically told to close, but the closure of those businesses meant other businesses were not making money, so it was not economically viable for them to remain open and paying staff.
"Never mind all the ones making them work regardless of furlough"
This is obviously wrong and against furlough rules, but difficult for the employee as they may bee compelled to do so to keep their job. It is not the employees fault.
"it was fine as a short term measure. Absolute piss take beyond 3 weeks"
The government hasn't allowed restaurants to open yet, and shops can't open until next week. It would have been immoral and resulted in millions of redundancies if they had stopped furlough after 3 weeks. If this had happened, the unemployed would have ended up on benefits so the government would have been paying them anyway, and probably for longer.