Yes, I've heard the same old " you don't have the big picture " excuses before and of course I don't expect any controller to actually admit there are good and bad controllers.
Of course there are & of course we have good days & days when "I could have done that better", same same pilots.
Why do you find it so hard to accept that there are more factors than you can see from the pointy end & on TCAS? Maybe it's actually true......
My arrivals sequence might be a nice "string of pearls", until the flow controller intervenes & tells me to "max him up", "loose another 2 minutes with that one", etc & so forth. The buggering around you're getting from me may be all to do with what is going on in someone else's airspace.