He had 3 choices.
1. Status quo & hope for the best.
2. Ramp it up to 500,000 men & drop more bombs on the jungle than all of WW2.
3. Get out! Just get the hell out!
Johnson had bad advice all around. Truman lost China & needed Ike to keep Korea. People kept talking about the collapse of all of Asia. He was damned if he did & damned if he didn't.
This (which is why I don’t really fault LBJ that much for the War) but in hindsight, GTFO was the all-around best option and his legacy would not be tarnished by Vietnam like it is. He’d be up there with FDR and Lincoln as others have noted.