You have two options
1: Stop playig Link and switch to a high tier.
2: Keep practicing with Link for months against Top tiers till you learn what works
If you chose 2, here's some advice:
Falco: This matchup really isn't that bad. Just jump over the lasers and spam bombs as you approach. For me at least, they seem more useful than rangs in this matchup. once you close in, don't get too close. be close enough so your jab hits but far enough so he can't grab you. then alternate between shffled nairs and jabs while he's shielding. Also throw in a shffled fair for extra knock back. Then, if you ever see him get hit by your nair, an attempted grab is pretty safe. if you get in a fair while using this jab aerial spacing, it's also pretty safe to d-smash afterwards between the fair and the d-smash, it should push him back far enough while shielding so he can't hit you after the d-smash and perhaps your shield pressure has eaten away enough so that the d-smash actually hits. Then you caneither tech chase or d-smash to dash attack combo. Now, this is if you succeed in approaching Falco. Sometimes those lasers just seem to ground you to the point where it's nearly impossible to move. Now You can usually jump out, but if you get hit by the lasers and Falco starts approaching, put up your shield. Watch to see if he will shl into a grab or an aerial. if he goes for a laser to grab, roll. if he goes for a laser to aerial, shield DI away from Falco as the aerial hits. Falcos' like to pillar Links' shields with the shffled dair to shine pillar. When you DI away with your Shield, Falco's shine will no longer hit you. They can't tell though so they'll still shine. Just shield grab after his aerial for Free combos. In most cases it's stupid to shield grab with Link. It works here though because the extra frames between the time Falco hits your shield to his shine allows you to grab him if you DI away.
Fox: Probably the most difficult, but still doable. Fox is a lot faster and can run circles around Link and his projectile game. In general, rely on bombs a bit more in this match up. Full jump a lot, and sometimes double jump while pullng/throwing bombs. Then, as Fox gets closer, or as you approach, Full hop Nair and jump out into a fair or another nair or out of your bomb throw. then use the same spacing and shield pressure as used against Falco.
Shiek: This is actually a really fun matchup just because you can combo her so well. In this match rely on both bombs and rangs due to Shieks ground heavy game play. A nice way to spam is to turn and run for a split second, then short hop turn and throw your boomerang or bomb. Every time you turn Shiek willl think your running and will approach, not expecting a projectile. Don't try to pressure Shiek's Shield like Fox and Falco. Her grab range is much better and Spacing in general fails. Only approach if you see a projectle hit. When she start to get close, jab and d-smash. If it look like she'll approach with a dash attack or a tilt, cc d-smash for nice combo starters. Really, watch out for the grab. Her tilt combos are easy enough to DI out of. but Chain grabbing can be a pain. At first, if the Shiek is CGing, DI up and a little towards Shiek. you should be able to jump out of the CG because of weird positioning and the Shiek usually won't realize she needs to turn to grab you since you appear in front of her. After a few missed CG's, the Shiek may realize she can u-smash you from your DI. From there, DI just aliitle foreward and you still appear to be in the same place but the u-smash won't hit. In genereal, this will reduce the chain grabbing to a 50/50 guessing game between Link and Shiek. Hopefully luck will be on your side.