Yeah, I do not see why people say Fox is good; he racks up damage well, yes, but he has very, very little KO options, and very, very weak attacks in terms of knockback. He has the weakest specials in the game and some of the weakest normals as well, but I guess we can attribute his speed and capability of racking damage fast, as well as his U-Smash being powerful still, that he's good. However, Fox is nowhere near the top, because you need to hit with the tilt of U-Smash for it to KO around 110%.
U-smash isn't hard to land as long as you're not predictable fishing it, especially considering that jab 1 -> jab 2 -> U-smash flows nicely with most of the cast (different %s for everyone, of course). If the opponent is shielding a lot because they except it, Fox can run up and grab, or even just run past their shields to condition them to not use it. Once the opponent stops, running U-smash let's him go in and KO (U-smash comes out on frame 8, same as Rosalina's).
You don't always have to KO with U-smash as Fox either. D-smash is viable against those with poor-mediocre recoveries, as it sends them straight forward. B-air comes out fast (frame 9 iirc) and you can use Fox's falling speed to cross up opponents: even if they shield, B-air has shieldstun to make it safe unless powershielded, and it also autocancels. And finally, U-air is still powerful to get KO's, and can be set up from a U-tilt (Fox has the fastest U-tilt at frame 3, tied with ZSS), Dash Attack (lasts from frame 4 -> frame 19, punishes most spot-dodges and rolls), or from a Side-B Illusion (unconventional, but SH Side-B works slightly better now that the landing lag was reduced).
Fox's weaknesses aren't his specials: although his side-b is the only good one, they don't compromise his game plan. All the other special moves merely assist his game plan: Blaster forces reactions and discourages running away from Fox (you just have to be less trigger happy now), Up-B is for pure recovery, and Down-B is for discouraging heavy projectile use and escaping juggles.
Fox's true weakness is when it comes to edgeguarding / gimping: the only safe option he has is N-air offstage. The others (B-air stage spikes, Illusion plays, F-air spikes) are all either difficult to do or require a good read, and they put you in bad positions if you miss them.