The Rebellion didn’t treat Luke that way. They didn’t hinge all their hopes on whether or not he showed up to help. Despite his abilities, he was still just one man, and one small part of a larger faction. The fact that the Resistance is so hyper focused on recruiting someone who, as far as they know, abandoned their cause years ago, and is hopeful that he’ll return, is naive and reflects poorly on them.
He’s still just one man, regardless of his powers, and it takes a long time to train a new generation of Jedi, so that’s hardly an immediate concern for the First Order. The line in TLJ when Rey tells Luke he needs to “bring the Jedi back” to stop Kylo Ren is really odd, since it makes it seem like Luke can just flip a switch and restore the Jedi after years of sitting around.
It’s also odd that Snoke is more focused on finding Luke than he is on destroying the Republic. His priorities seem backwards. He and the First Order have much bigger fish to fry than an inactive Luke who might be a potential threat in the future, yet Snoke talks about finding Luke like it’s the most important step in winning the war. But if the Republic and Resistance were destroyed, Luke coming out of hiding would be a nuisance, at best.
I do agree, though, that TFA sets up certain plot points that TLJ had to work with, particularly involving Luke’s exile. And TLJ often wrongly gets blamed for creative choices already established in TFA.