if there was a time when we universally had good capacitors?
Not really. Older caps were often 'smaller', or lower capacity, while same volume. Modern caps can have a higher capacity in the same volume, but I doubt they are any worse. (I am 74 yrs old).

What does happen a bit more today is a squeeze on safety margins in order to cut costs. For instance, 240 VAC is ~340 VDC peak. People used to use caps rated at 630 VDC for this; today many cheaper designs use caps rated at only 400 VDC.

Yes, 4 off 100 uF caps in parallel can be better than 1 off 400 uF. Lower ESR for a start - all things being equal!

Cheers
Roger