Robin's jab can followup (most commonly into grab) or can use the full extent of it of the jab itself: both finishers send opponents far enough to get his projectiles ready, while his rapid jab deals on racking damage and fire deals on KO'ing. Shulk's in the meantime, is simply a worse version of Ike's jab.
I feel like people have underestimated the projectile prowess he has. His thunder variants are versatile, his arcfire covers the ledge pretty well, and Nosferatsu... okay it is not something to write home about but it gives Robin the only attack damage-steal move in the game. His tomes when he lost (which includes his Leven Sword) gives off more pressure when used as projectiles. Losing them in the first place is a hindrance, but it is not entirely too large of a downside. Many of Robin's tools (which does include his Bronze Sword) combo to eachother well.
Not sure why Robin is comparable to Pokemon Trainer. PT has mechanics that are designed to hinder him, while his Pokemon suffers from some sort of hindrance, as each has some of their own flaws since they are separate-ish fighters. Charizard is considered to be a below average to medicore character, while Ivysaur is considered to be one of the worse characters in the game as a standalone fighter. PT's gimmick is far worse than Robin's, and characters not top 31-ish is considered not super relevant in the game anyways.
Was unaware of the jab to grab, assuming it's true and not just a mix up. Frame 4 jab with an faf of 32 leading into a frame 7 grab? No idea how long hitstun for jab lasts but it's not a tether grab so it could be possible. Wind jab only does good damage at low percents and usually only on fast fallers. Everyone else can di out rather easily. Fire jab is better but also has fewer uses and while it kills, it's also rather late.
Thoron is pretty crap, best use I ever found for it was if you manage to get your opponent to the percents where it kills, it usually works as a good landing coverage to guarantee a kill unless you're fighting someone like Kirby or Puff who have really low landing animations that duck under Thoron. Thunder is just meh, good for peppering opponents at its max range but that's about it. Elthunder is a more 'standard' projectile and Arcthunder leads into other stuff making it the best one. But for a chargeable and storable projectile, it's nowhere near as threatening as Shadow Ball, Aura Sphere or Samus Charge Shot.
I compare Robin to PT because as I said, they are focused around gimmicks that ultimately hold them back. PT with switching, stamina and type effectiveness and Robin with an overly high focus on his powerful aerials. Those aerials explain why his movement speed is crap, why they're slow to come out compared to most other moves including other sword moves and if he runs out of it then your opponent knows you're hardly a threat to KO them for the next few seconds. Robin doesn't have it as bad as PT partially because Sm4sh is ultimately more balanced than Brawl but they're both in a similar tier position, the lower end of mid tier, verging into low tier.
Oh and holding onto a discarded item immediately tells your opponent that all you have to work with now is 3 projectiles (item toss, Arcfire and the Thunder spells), a command grab, a non threatening recovery and z-drop aerials. It's not always an immediate boon to have a discarded item in hand whenever one pops up.