you say this as an absolute truth - but we know it's not. it's a gradient.
For example - say we took a lane off of rural Highway 10 between Brampton and Orangeville and replaced it with bike lanes. Do you think it's impact would be negligible and would overall improve economic output?
Obviously not. Nobody will be cycling from Orangeville to Brampton.
The example is a bit facetious, obviously - but there are degrees in between. On one end you have projects like Richmond-Adelaide and the waterfront trail extension across downtown - clear, unambiguous net positive lanes with heavy cyclist use and minimal impact on traffic. and the other, you have theoretical projects like the one I describe which would be laughably ridiculous and clearly not beneficial - but there are a million degrees in between. Bike lanes are not always absolutely beneficial. How many people on the road are making trips under 5km? how many destinations are available in cycling distance? employment opportunities? Is a lot of the traffic commercial vehicles or personal vehicles?
If you can add bike lanes without taking out existing capacity - it's always a win. But when you don't have that space, it needs a closer look of benefits vs. impacts.
For example - Bloor through central Toronto, while technically 4 lanes before the lanes, was mostly operating as a 2-lane street anyway given the huge number of parked cars and illegal stopping occuring. Converting it to a 2-lane road with bike lanes had a very minimal capacity impact for vehicles but provided a safe cyclist space in an area where it's easy to make trips by cycling with shopping, employment, and everything else within 5km for most residents. A win-win.
Further west though, into Bloor West Village - employment is more dispersed. Car volumes are much higher, and the road actually operates with 4 lanes of capacity at all times. It's harder to cycle places as more destinations are simply outside of cycling distance. The lanes effectively cut throughput capacity by 50% by removing a lane, but don't offer a viable alternative for many types of trips that locals make. Maybe it doesn't work out as well.
It's a weighted decision that has to be made - and is far from a universal one.