From what I understand developers started building in anticipation of Amazon coming there, and that investment is now in question.
New York's economy is plenty diverse. There's real estate and Wall Street, sure, but there's also legal services, advertising, media, health, education (NYC has the largest student population in the country), hospitality, tourism, etc. This is no one company town like Gary.
It would be a good thing to not concentrate all jobs in Manhattan.
Also, if you walk around LIC, it's not as developed as you might think, sure there are huge buildings, but they're next to empty lots & industrial spaces. It's largely a desirable area because of it's proximity to Manhattan, not really anything intrinsic about the neighborhood.
Putting jobs in LIC will still force workers from the non-Queens sections of the metro area to go into Manhattan and then back out to Queens. Even the LIRR can't really serve LIC, because it's impossible to build a station that serves waterfront LIC that is on the way to Penn.
And it's also ignoring the fact that a lot of people already live in Queens, and that LIC specifically is connected to Brooklyn via the G.
It's not an ideal situation, but it's a chicken & egg problem, there's no reason to build commuter transit there without employers and employers don't want to be there without that transit, so the Amazon deal would have done a good amount to break that stalemate.
In what alternate universe is this? Queens is hardly Camden or Detroit. The neighborhood in question has 40+ story office and residential towers sprouting up like weeds. Queens is at a record low employment rate ever since this started getting tracked at the county level: https://fred.stlouisfed.org/series/NYQUEE1URN. And there are similar statistics for the metro area. It is unclear to me that New York City needs to throw any tax credits for jobs when we are running probably very close to full employment.