Improving a "very bad neighbourhood" in the sense of "poor person's neighbourhood" tends to be undesirable for the people who are priced out as a result. Owners will do ok financially, but rents will rise, forcing many to leave the place they are settled in, may have grown up in, and often where their extended family lives.

If the alternative is to keep it a "very bad neighbourhood", I don't see how how the situation is not at least even. (Unless "very bad neighborhood" was an exaggeration. "Poor person's neighbourhood" certainly wasn't what I imagined, but I live in a place where most "poor person's neighbourhoods" are pretty good...just poor, that's all).

Yes, I am in favor of improving it. It's just that if we're talking about 6th and Market, getting it anywhere close to what we think of as "gentrified" is a long, long game, especially in San Francisco. It's a legendary corner.

But as others pointed out, the spot in question might not actually be right there, I was just commenting on the area mentioned by the parent, to add context for the non-SF people.