Oh my god, there are far too many to name and I'm always looking for someone to listen to my ranting about terrible transit. Sorry, but for asking this question you're now going to get a very large wall of text.

1: A lack of signal priority. Countless hours of collective human time have been wasted in transit vehicles waiting at completely empty intersections for a red light to change because the traffic signal uses the state of the art technology called a timer.

2: Terrible right of way. Way too many transit agencies place their transit lines not based on where demand is highest or where transit will be most effective, but just where land is cheapest or where the transit agency already owns. The principal rapid transit line in my city runs along a river because the city already owned the land, but it means that literally half of the area surrounding the transit line is just completely useless because it's water. Highway median transit is another example of this, which can often lead to…

3: Terrible land use surrounding stations. Almost without fail transit stations in North American cities are surrounded by parking lots, highway interchanges, or just straight up undeveloped land.

4: The North American light rail obsession. Nearly every single new or recently built rapid transit line in the US or Canada is done using trams, often running partially on the street, with absolutely no consideration for if this is the right transit solution for a given city. Link in Seattle is a good example. It's absolutely absurd for a city the size of Seattle to have light rail. A city of 4 million people in any other developed nation would have a proper metro, but because Seattle is in America it gets a shitty light rail.

I may return to update this later but this was all I could write for now