Link's Up-B OoS isn't better than T.Link's lol. When you do things OoS it's often times for safely getting out of shield. Yes, Link's kills, but it's also a single hit. Once it collides with a shield Link is free to be punished. T.Link has multiple hits, so it often shield pokes should people opt to shield it, and he can move around in it. I don't know how many times I've had people try to shield grab me and I'd have crossed them up. N-Air OoS is comparible really, but if we're really talking about who's N-Air is actually better the answer is T.Link. It's been better since Melee. Link's grab OoS is only better because the grab goes farther.
D-Throw is also comparible. Both characters have guaranteed kill setups with this throw. T.Link's D-Throw > Up-B is plenty reliable, but it's character and damage specific. If you can't hit with Up-B after D-Throw you're definitely able to hit with something else. Most of the time that something else is a guaranteed F-Smash, which is better than landing an aerial Up-B. Other times though it's a F-Air or D-Air, but that's usually only when the character is too light, too floaty, or has high damage so using these moves usually has the same effect as landing a Up-B or F-Smash anyway.
Link's bad mobility definitely effects his viability in a lot of matchups. Once you get into Link's bubble he's going to have trouble. He doesn't take pressure as well as T.Link (despite what you've been led to believe). Both characters have terrible rolls so they're not usually viable options of escape from pressure. T.Link however has a wavedash worth using, and it's very effective for escape and for punishing. when used OoS. Their combo ability is about the same, but T.Link's kit starts them better. Fire Arrows, boomerang, and especially bombs for T.Link is a ticket for T.Link to charge in and start a combo. Link's bombs can do the job at low damage, and boomerange all the time. Arrows knock people away but that's also fantastic for Link because it lets him gimp without endangering himself. Once they're in the combo though, Link certainly does have the easier time because his Dash Attack does all the work, but T.Link has U-Smash for a similar effect and his U-Air juggles last longer because of his mobility, and they convert into Up-B kills on a lot of the cast.
Link's tools are also really not unbeatable like you make them out to be either. Almost anyone can just go through his boomerang with some kind of lingering hitbox. Mario, Fox, T.Link, etc can literally all N-Air through it. Many can N-Air through an uncharged and partially charged arrow. Bombs can just be caught wavedashes and just be thrown back. All of this applies to T.Link as well, but his boomerang having much better angles as well as going farther and returning slower gives him a lot of stage presence. There's almost never a time where T.Link doesn't have at least two things to worry about on screen.
Also Link definitely unfavorable matchups. Falco, Mario, Fox, Mewtwo, Lucas, Meta Knight and maybe/maybe not Lucario are unfavorable for Link, then after that most of the others are closer to even than Link having a full advantage, save for some obvious matchups. And that's how T.Link has it too, just with different characters, and he probably has a more even matchup spread.
This post isn't being made to tell you you're wrong about Link though. Link is definitely a strong character, anyone who thinks otherwise is either delusional or hasn't seen or played against a good Link player. But you're definitely not giving T.Link the credit he deserves. He's a very good and highly viable character. The biggest difference between Link and T.Link is that Link doesn't take that much time to learn in comparison. T.Link takes a decent amount of time to get used to, as his setups aren't always immediately clear like Link's are and they vary a lot more from character to character.