Clark isn't a leader of anything right now. He's still isolated himself and is clouded by self doubt and the weight of the mistakes he continues to make.
Have you been watching the show lately? There was that great scene toward the end of last season where he had a whole bunch of Justice League and JSA members on screens and was giving them this great pep talk. He had clearly become the leader of the superhero community he had formerly renounced. No, that's not something they can show every week, but that's because budget and logistics preclude them from using the whole League regularly; but we'll be seeing plenty of them in individual appearances over the course of the series, as with Carter Hall this week (and he was clearly acting on Clark's instructions).
And who says having self-doubt is incompatible with being a leader? Heck, James T. Kirk's constant self-doubt and introspection were part of what made him a great leader, because they kept him honest and able to rectify his mistakes.
Miller and Gough were still the show runners when he got the job at the Planet, I want to say that happened in season five.
No, season 5 was when Clark went to college. It was Chloe who got an internship at the
Planet in season 5. Lois became an investigative journalist at the
Inquisitor in S6 and was hired at the
Planet at the start of S7 (actually the second episode,
"Kara"). So yes, we often saw Clark at the
Planet from S5 onward as he interacted with the characters who did work there. But Clark didn't actually become a
Planet reporter until after Lana left Smallville, i.e. the start of S8 (
"Odyssey") -- right after Millar & Gough left the show.
PSW have actually been pretty faithful to Gough and Miller and haven't changed much.
If by "PSW" you mean the new showrunners, I think they've changed everything. The early part of S8 in particular felt to me like an aggressive renunciation of the limits M&G had imposed on the show. Clark and other characters frequently criticized his insular behavior in earlier seasons, his former refusal to embrace his heroic destiny. That sounded very much to me like authorial insertion, the new showrunners expressing their frustration at the limits that had been placed on them before and that they were now free to cast aside. To quote the
Smallville Wiki's summary of "Odyssey," linked above:
Clark responds saying it is time he stopped holding onto a life on the farm that was gone a long time ago, and begin to accept his destiny.
That was a mission statement for the new showrunners right there, and a turning point in the show's storytelling.
M&G were in such a rut that by the end of season 7, I couldn't even bear to watch anymore. Heck, I would've given it up years earlier if it weren't for my adoration of Kristin Kreuk. But by late S7, it just became so odious and awful that even she couldn't keep me watching. But with S8, the quality of the storytelling improved immensely and it's stayed strong ever since. So with the departure of M&G, it's gone from painfully bad to good and sometimes excellent. I don't know what benchmarks you're using to evaluate it, but from my perspective, it's a profoundly different and much better show.