I'm actually going to go with Hunybear here and say that Link struggles very hard against Foxes who 1.) Have solid shield pressure / tech in general, and 2.) Know how to crouch cancel effectively.
If a Fox meets criteria 1 and 2, and Link is caught in his shield, there is literally nothing Link can do except roll or pray for the Fox to mess up.
When Fox is dash dancing right outside of Link's grab range, and Link pulls out a bomb, Fox can run in and punish. If Fox is at low percent, and he's quick when acting out of crouch cancel, Link has to either pray for a forward smash to get Fox out of crouch cancel range, or hope that the Fox does not know that Fox can escape bomb-->grab from Link at low percent.
I mean, I've beaten decent Foxes with Link. However, when they're familiar with the matchup, they basically just dash-dance until Link messes up, and then go in really really hard and stay as close to Link as possible.