Yea a I noticed that Fox seems to get gimped much more often than Wolf.
Keep in mind that Fox's weight was lowered a bit in Ultimate, from 79 to 77, so he does take more knockback. Fox has also been progressively coming closer to a Melee character's falling speed after Brawl. Ultimate Fox clocks at a fall speed of 2.1 and regained his 0.23 gravity from Melee. Fox not only falls the fastest, but he reaches his fall speed faster than anyone else.
And as noted already, if Fox is forced to use his Fire Fox, it's heavily telegraphed. Getting hit by it is dangerous, but for some characters, especially characters with disjointed aerials like most weapon users, it's not that risky to hit it. Case in point: Lucina. What doesn't help is that Fox Illusion is slower than in the previous games. The rundown is that Fox's recovery is very telegraphed on top of being linear, and therefore, predictable at times. In contrast, characters like Captain Falcon, Ike, Luigi, Mario, Roy, and Wolf have linear and predictable recoveries, but theirs are much faster than Fox's or very fast like Luigi's and Mario's Super Jump Punch. That said, they have their own issues that Fox might not have when it comes to recovering.
Fox's recovery moves also aren't as threatening as say, Ness's PKT2 where you're probably going to die if you mess up and get hit by it. Wolf's recovery moves are already noted to be threatening, especially if you get hit by Wolf Flash's sweetspot and aren't prepared for it. That thing does 20% with the spike hitbox and 15% with the not spike hitbox. Falco also can spike with Falco Phantasm which while rare because it is kind of hard to hit with it, does deter some people from trying to intercept it off-stage. Fox Illusion on the other hand would pop you up while Falco Phantasm could lead to a spike or a gimp.
Fox doesn't really have any threatening aerials he can use when he's trying to recover. With his fall speed, Nair, Fair, and Dair are probably too committal and burning a jump might not be worth it for him to rise with those aerials, Uair probably wouldn't really work in most situations and I wouldn't be surprised if he could SD himself while trying to cover above him with Uair, and Bair is not going to happen unless Fox finds a way to turn himself around. Mewtwo and Wolf can threaten with rising Fair and with their projectiles. One key thing is that Fox's Blaster lasers don't do knockback. Falco and Wolf don't have that problem, we've seen ESAM, VoiD, and other Pichu and Pikachu players cover their already good recovery with Thunder Jolt, items and Pikmin being thrown from the blastzone by the Links, Olimar, Peach, ROB, and Snake not only annoy, but interrupt and add more for the opponent to deal with, and being unprepared for a charged projectile from Lucario, Mewtwo, ROB, and the Samuses can kill the opponent if not do a lot of damage.
If Fox had Impact Blaster, basically Falco Blaster, but if it couldn't be fired continuously or 64 Blaster without the ability to auto-cancel, Fox could probably do something like tag his opponent with a laser to stun them a bit in order to buy time for Fox Illusion.
Once again, though, that's when Fox is off-stage and recovering. Fox's on-stage performance and capabilities are more than enough to make up for his issues with his recovery.
Not to mention the move has serious launching power.
I tried to look for it, but I can't find it. Ultimate's day one patch changed a bunch of things and I swear I saw a tweet mentioning Fire Wolf was among them. I can't remember who tweeted it and I don't remember when. Its last hit used to have lower base knockback and higher knockback growth. Before the game was released, people were talking about how Fire Wolf could kill very well and earlier than what it can do now.
Some of the day one changes.
Speaking of patch changes. 2.0.0 apparently broke Olimar's Smashes and not for the better. Maybe we'll get a hotfix if this becomes a big enough issue.