I think it's important to remember a few things when you see that street and the park sitting empty--
1) It's been REALLY hot outside
2) This is an all volunteer initiative, with city agencies granting permission but doing none of the work, donating a sum total of 7 large planters (but not the soil or the plants), doing none of the cleaning, plant watering, programming or anything else. In other words, this is a true neighborhood initiative. I'd say if you don't think there is enough happening there, then it's up to you to change it. And you can.
3) The street is closed 24/7 so that it can serve as an overflow when the street is most crowded -- afternoons when the weather is nice, weekends, etc. In a perfect world we would just close it then, but it's a logistical nightmare to close it -- clear out the cars, put up the barricades, etc. It's much easier to just keep it closed 24/7.
4) Sure, there are times when the park is empty and the closed street seems superfluous, but the street is actually much more shaded, and thus cooler. Also it allows some space for younger kids to bike and play without getting hit by baseballs, soccer balls, etc. And when the park is crowded, which it often is, this will hopefully provide a lot of overflow space.
5) So far I've already seen a lot of activity on the street in the cooler evening hours including elderly residents just enjoying some air, families hanging out, games of catch, kids learning to ride bikes, skateboarding, etc. But the street has been closed for less than a week. Give it time to become part of peoples' routines.
As for the "small patch of astroturf" well, there was more than twice that amount but someone stole all but what you see now. So, blame them.
Finally, I'm not trying to be confrontational, but maybe it's inevitable. I have to admit, I really don't understand why there is any opposition to this project. This neighborhood has a TON of parking. It just also happens to have a TON of drivers. So, yes, parking is at a premium. And all those car owners know well and good that it's a tough neighborhood to park in and yet they chose to buy a car (and yes, I said "chose" -- if you need a car even though you have such great transit options then you've made a choice to live in a dense neighborhood and own a car). And yet we are supposed to feel sorry for these drivers because 50 or so parking spaces got lost for 2 months?
But really, would anyone argue there is TOO MUCH recreation space in Jackson Heights? I don't understand why parking is the holy grail. I really don't. Do car owners have some divine right to unlimited free parking spaces that I didn't know about?