It's true that unless you PS (power shield) his smashes (especially Dsmash) they can't really be shield grabbed... Luckily, Marth has a lot more OoS options than just shield grab. For example, Marth's Up b OoS has more horizontal range than his shield grab and it is just as fast (when it comes to the first hitbox of Up b coming out) as shield grab if you time the jump + Up b as fast as possible. If Wolf spams laser, don't run, walk instead and PS the lasers. You can't shield during the first 17 frames of your dash. Marth's walking is pretty good too. Try Wolf yourself in Training Mode or something and analyse the amount of lag the laser has. From a CERTAIN distance you can always PS and run side b him OoS (out of shield). If you're too far, just PS and keep walking to get closer to him and reshield or something. Also be aware of your shield health. One thing I've noticed is that approaching Wolf with an unhealthy shield can sometimes be a pain, which can happen often enough when you're shielding lasers all the time (ESPECIALLY if you're not PSing them). So if your shield is running low, wait until your shield becomes healthier and then approach him once your shield is healthy enough.
Wolf's Dsmash is actually a terrible way of dealing with Marth's Fair. If anything, Wolf's Fair and Bair should be the moves that are threatening your Fair, not his Dsmash because if you're Faring correctly because they're the things that outrange our Fair and have little lag (in Fair's case, only if he autocancels it, which he can do from a short hop). If you space your Fair around his head, he can't Dsmash you. You can also abuse the extending of the hurtboxes of his moves and space a bit outside so that you hit him without hitting you. An advantage Marth has over almost everyone is just the disjoints which makes him outprioritise almost everything if spaced well (be aware of his hitboxes having low duration though). If he spams smashes, then it's obvious that they're really predictable and if you shield a smash then you can always shield release and DB OoS on reaction even if it's well spaced unless something like him pushing you off the edge happens.
It is completely true that jab is unsafe on hit at low %s. The good thing is that Dancing Blade is just as fast as jab start-up wise (both are 4 frames) and is pretty much always safe on hit (other than shields). That doesn't mean jab is useless though. Jab becomes safe on hit at higher percents and can be decent for SITUATIONAL stopping aerial approaches of the opponent against you and for forcing the opponent to the ledge when they're trapped near the edge of the stage.
Also, Fthrow combos are completely guaranteed on Wolf at 0 % (at least you can do 2 Fthrows to Fsmash, 2 Fthrow to Dair may actually work too, which unless he has godlike SDI will kill him offstage because of his slow up b and the by far the worst meteor cancel in the game). He can't shine out of those things at 0% if you're timing right. At other percents, it's just tech chasing which is hard to explain and is better learnt by just experiencing (still can lead to great strings which can put a lot of damage on him if guessed correctly which isn't too hard because he doesn't have that many DI options). But if anything, his DI options should be helping him a lot more to get out of the Fthrow combos than what his Shine does. However, at mid percents I do like Uthrowing Wolf because Wolf has a terrible fast fall (barely faster than his normal falling speed), which makes it not too hard to juggle him with moves like Uair when he's above you. Even if Wolf's shine does give invincibility from frame 1, it's far from lagless and if you shield it then you should always be able to punish him for hitting your shield with the Shine, so mixing up with actually baiting out the Shine isn't a bad idea. The Shine isn't a very hard punish either, it only deals like 3% damage IIRC.
If you want MU ratios of this MU, many say this is an even MU. While I may not entirely agree with it being exactly even, it's certainly by no means far from it and just because Wolf is mid tier doesn't mean this matchup is "easy".