A pet peeve of mine is that google maps doesn't show most transit routes on the map. There is a transit layer you can enable, but it only shows metro and light rail, not buses, brt, trams, ferries, etc.
This is a problem with GTFS. Firstly, that GTFS has separate enumerators for trains vs. buses, and only shows stuff that identifies itself as trains, but also because most agencies do not provide route shapes that are good enough to display. Often the routes run right down the centerlines of roads, cut through buildings at corners, etc. There would have to be a revolution in local government agency GIS quality control before it works right.
My pet peeve is that there is no hybrid bike/transit routing option. If you choose transit, they assume you are pedestrian. Maybe the option is there and I just have not found it.
Citymapper at least tries, but is still bad for bike+public transport.
I look at the options that Citymapper gives and then have to recalculate the route, in my head, correcting for wrong decisions about where I'll have access to a bike.
(Yes, it'll be quicker if I cycle my own bike from my home to the nearest station. No, I won't be cycling a hire bike 111 minutes away from its closest docking port.)