> I think mainstream analysis is that を is considered to not always mark the object,

But even in English we can say things like "fly the skies" or "walk the streets", which map reasonably well to how を is used. When it's used for sentences like 自転車を盗んでいるところを捕まった (roughly "caught about to steal a bicycle") however it's harder to understand it that way. It's not the ところ that was caught, but the (implied) topic, probably "I" with no other context