"Lower your home's sale price by 10% or 20%" is bad framing. For one thing, it's speculative: there's no way to tease any particular nearby building project's effect out of the thousands of other factors (most of them orders of magnitude more significant - like local and temporal macro-economic conditions) that effect home prices.
For another, it ignores potential positive effects. If new building improves local economic conditions, then your home's price (still speculatively, mind you) could equally as well be increased. (With relaxed zoning you might hit the lottery, and find that your lot is worth building an apartment on, and never have to work again!) Focusing entirely on potential negatives is unfair argumentation.
Even apart from price, this approach places emphasis on (potentially) negative second-order ("traffic"), while ignoring (potential) positive second-order effects. In my case I'd straight up trade a 20% decrease in my homes sale price in twenty years (I'd still come out $$ ahead) for twenty years of living near a re-vitalised (instead of currently derelict) commercial strip.
I don't think it'd work out that way: I think living walking distance from, say, a nice coffee shop, pub, grocery store, and cinema (those buildings already exist, by the way, they just need to re-open, which can only happen if more people are nearby) would increase my home's eventual value. That's speculation, too, but equally worthy of consideration as the negative cases.