So to respond to the original post, I will be leaving constructive criticism for your Link. I'll explain things that I believe can help you win games, and things that could cost you games, or habits that would give up neutral or put you in a state of disadvantage. I hope you'll read through it all because I'll be giving a very, VERY in depth analysis of your game play. This is not to $%!& talk you but rather to improve your game play exponentially.
The first and most important thing I noticed that you REALLY must work on if you want to improve is your short hops into fast fall aerials. I see a lot of full hops at moments where a short hop aerial could have put you in a state of advantage, or forced Ness into retreat or shield at minimum. I also stress again to practice fast falling after reaching the apex height of your short hop.
Arrows: These projectiles are generally BAD to use in the middle of neutral game. They take too much time to charge and are only really a viable tool to edge guard with if the angles are correct for it or the matchup makes it free (like Ike using Side Special to recover). You spend a lot of time and space to charge an arrow and allow the Ness to do as he pleases in the process, also leaving yourself exposed to an aerial PK Fire, repeatedly. Lucky for you, this Ness you played didn't catch on to that. These arrows you put out in neutral could be another boomerang, which is a clearly superior projectile to the arrow, or could be you pulling a bomb, which is one of the best non attached attacks in Smash Ultimate overall.
At 2 minutes and 5 seconds into the video, I noticed you put Ness off stage at a high angle. You stood at the ledge and waited for him. This is giving up valuable time to pull out a bomb. Remember to always pull bombs whenever there is a FREE chance to do so, such as this situation I'm explaining. You could have had the bomb ready in hand and could have done a jump and thrown the bomb up to intercept Ness and put him back off stage and pull another bomb to continue the process until you received an appropriate launch angle to do a full edge guard. In the end, it's still okay because he didn't airdodge through your Up Special.
Stationary projectile use is dangerous in higher level play, especially against players like myself who are very reaction based because we play a lot offline with high level players. Standing still when throwing a projectile can easily get you punished by rush down characters (like Fox or Zero Suit for example) or allow other projectile characters to approach while also disabling your projectiles with your own. The best thing to put into practice specifically when throwing your boomerang is to move while you do it. All you have to do is jump left or right, then toss out the boomerang while you're in the air. This also gives you MANY more options of overall angles you can throw your boomerang in. You wont be left as open and vulnerable if you put this into practice. This is also very important projectile practice because it allows you to evade and play the keep away game more consistently if you must.
The bomb is the ultimate utility Link has. I notice that you have a habit of instant detonation, even if you throw the bomb past your target, where they are no longer threatened by the blast hitbox of the bomb, as seen in your video at 2 minutes and 45 seconds. Links explosion animation is very long lasting, so every time you perform this bad habit, you might as well tell any good opponent "come take this stock for free". I highly recommend putting this habit to the side. Also, just like the boomerang, it is best to pull your bomb while approaching or playing keep away by pulling it while you are jumping left or right through the air, because just like the explosion animation, the bomb pulling animation is also super long, and leaves you very vulnerable. You want to be in motion so that you are less likely to be hit by something, or you could use this technique to chase an opponent you just hit while at the same time pulling you bomb out for use,
SOMETHING TO LEARN: I highly recommend that you learn how to do bomb aerials. This is done by jumping, then pressing the grab button while you are holding the bomb (this will drop the bomb and is called a Z-Drop), and then immediately after pressing grab, do any aerial, which will not only throw out a hitbox, but catch the bomb. Essentially what this means is that you can do aerial rush downs while holding your bomb in hand, and the best part is, the bomb itself has a hitbox during the Z Drop. You can also short hop and throw the bomb down to put out a hitbox when you are ontop of your shielding opponent, then do a quick falling neutral air fast fall, catching the bomb and being able to do an overshoot zdrop neutral air, which will put you in a safe reach from the opponent or hit them because they dropped shield.
I also really recommend practicing utilizing Link's long lasting neutral air hitbox effectively off stage for edge guarding. Learn to do Smash Bros Melee style edge guards to. When you are hanging on the edge, and your opponent is recovering, it is good to sometimes do a ledge drop, then use your double jump with a back air to catch the opponent for the edge guard, then use up special to recover. Also learn to use bomb recovery. Very important. There are youtube videos on how to do that. You can also Z Drop the bomb off the ledge onto the heads of recovering opponents and then blow it up. Throwing it up while chasing off stage opponents is also a good option as it will cut off some recovery options on the way back.
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All this being said, I really hope you take the time to read it and understand these things. I came into this game with the focus of perfecting this character, and learned to play at a super high level in 2 weeks. You can see some of the things I'm talking about by
CLICKING THIS TEXT for a combo video I made or
CLICKING THIS TEXT for a twitch highlight video I made. If you have any questions about Link tech, or how to get better with Link in neutral, you can always send me a private message or find me on social media or even on twitch. If you also need a practice partner who can actually improve your Link quickly, I'm the perfect guy to play with for that. Link is 1 of my two mains and has been complimented by a couple of the best Links out there.
Good luck to your Link and I hope you continue practicing the character with the intent to grind and improve.