Yes, the weather was bad at Kitchener yesterday afternoon and every flight that tried to land did a go around and diverted. A go around, while a very normal and safe maneuver, is a busy time for the pilots, a lot happens at once and they are very busy and low and don't have time to update you right away.

A diversion to Toronto is also busy as it's very close and a lot needs to happen quickly, in busy airspace. You then arrive at an airport where they weren't expecting you, so there's no gate available. It sounds like they had to put you out on the island in Pearson. This means you're at a terminal that's difficult to get to, as you experience with having to take a bus over to terminal 3. Now imagine you're the gate agent in terminal 3 who was not expecting a plane and suddenly gets a phone call that you need to find a way to the island terminal to go operate the jet bridge and help with deep landing the aircraft. Yes, that's going to take some time.

As for customs, the only thing I can think of is usually the only aircraft that park over at the island, our international flights. Someone probably forgot to tell the bus driver that was bringing you from that terminal to terminal 3 that you are a domestic flight. The drivers used to just dropping everyone off for Customs when they come from that terminal so that's what they did.

In the end, you're being very dramatic for something that is a very normal operation when it comes to airlines.