If Luke hadn't been turned to dust then, he could do what the Avengers had done in 2023, and create a Quantum Tunnel.
With the Pym Particle, his clone, and his various abilities, he would definitely be able to collect all the Stones and do the Snap.
Save people first, deal with the backlash later.
If he was the one who died, and most of the Justice League and the Avengers were dead, the chances of the rescue plan succeeding probably might not even reach one in 14 million.
Thus, Luke could only do his best to lower the risk of a backlash as much as possible, and wouldn't give Thanos a real chance to succeed.
He had already killed this guy in 2023. Now that he had boosted his strength, there was a good chance he could send Thanos packing.
As he was thinking that, the car arrived at 177a Bleecker Street.
In the eyes of Luke and Thor, the New York Sanctum was just an ordinary, inconspicuous building.
