Hey, I find Link's D-Smash extremely useful on opponents who don't perfect shield. It's a go-to attack because it pushes the opponent away and applies heavy shield pressure. I think Link has one of the best shield breaking capabilities in the game. Ganondorf, D3, Marth, Lucina and Bowser definitely beat him, but Link can actually break shields with relative ease if you use him right.
When opponents aren't close enough (and don't have long grabs) and have to shield, Link finds this as a solid opportunity because since the opponent is too far away to grab and is pushed away, all the end lag in his attacks (except Spin Attack) won't matter if the opponent is too far away to retaliate. If they try, Link can spot dodge, grab or roll away.
Link isn't the fastest character, sure, but that surely doesn't hinder him from being a mid-high tier. He does get defeated by some characters, but characters like ROB would have a tough time against him.
Oh, and I'd like to mention that Rage doesn't affect Link aside from his smashes and tilts. He actually still has his combo ability and yet with more knockback, which actually doesn't affect him with his long ranged attacks. I've actually killed around 80% damage with Link's F-Smash on just 87% rage, and it was on a Bowser Jr.