Rambo is a period piece, plain & simple. The sentiment of the concept is outdated. The character concept is that he's a jilted, emotionally damaged, rogue ex-commando, with a war hero's record, who no one respects as such. Long hair or not, if people saw a man today who had clearly been in the service, nobody would be dumb enough to treat him like shit
So the notion of making a show about him in post-Vietnam USA is I'll conceived. The only show that would work at all is either one set during the war, or one set many years later when he's the boat ferrier from the last movie, wandering foreign lands, when his history beyond being a war machine is long behind him
Frankly, a Bourne series with a recast Jason Bourne would be much more relevant.