Stephen Avenue is fine for bikes + pedestrians. What is missing is a commuter bike route that moves east-west. 9th, 6th, 4th, or 5th Avenues are the correct answer for these, a one-way couplet would work. The bonus is these avenues are all 4 -6 lanes wide and are largely only busy 3 hours a day, plenty of extra capacity. Plus you get the light timing too as the city has so far proven to be unwilling to inconvenience drivers through better light timing for pedestrians and bicycles on popular pedestrian / bicycle routes. These would give commuter cyclists all the perks that downtown drivers get of high-speed, green wave timing.
But there were reasons Stephen Avenue was selected for the network over these other routes, with one reason being that it's better for low-speed, casual cyclists. Another reason is that Stephen has more destinations. Both are good reasons.
However, by far the most definitive reason was that the roads and transit departments as well as political opinions of Council couldn't fathom a world where bikes ride on any other avenue. Even now, with some 30-40K fewer downtown jobs and less traffic all around (except bikes and pedestrians) it would point to revisiting this question, as 9th, 6th, 5th and 4th are more over-built for car traffic then ever. There is capacity to spare, which should take the wind out of the sails of the groups/people opposed to another avenue. However, this line of thinking is also naive; it vastly under-estimate how car and peak-hour focused our planning, transportation and political cultures are here.
In an ideal world - one which I am optimistic may come sooner rather than later - Stephen Ave and other avenues will have bicycle infrastructure. We also would prioritize pedestrians, bikes and transit over everything else in the core (especially considering those three groups combined are the majority of inner city commuters). Car trailing green turns vs. leading green turns, shorter signal timing to minimize pedestrian waits and reduce car speeds, wider sidewalks and bump outs, bike lanes and cycle tracks, BRT lanes and so on. All the solutions have been invented already, they just need the political and cultural will to implement them, which is far harder to align.