3. Rosalina vs tink is pretty much cancer
Characters without projectiles feel this way. Fast melee characters feel this way. Heavies feel this way. Lightweights feel this way. Everyone feels this way.
Adjusting your approach and weighted options is important in very polarizing matchups. This isn't a 'toon link' issue, it's a player issue. Just because you have to adjust to defeat a certain character doesn't mean your character has a bad matchup against them, it means you can't fight them the same way you'd fight most other characters.
It's like saying reflector characters counter Toon Link - no, they don't. TLink's reflected stuff won't really make it back to him aside from Boomerang and Arrows, and fire arrows won't be very effective once reflected. Boomerangs suck when they get reflected, but if you NEED to use the boomerang and cannot adjust to not using it as much vs reflector characters, then that's an issue with how a player is playing TLink. It's like Lucario feeling reflectors counter him because aura sphere can be reflected - just don't rely on aura sphere in that matchup.
Challenge yourself to try different things in matches, rather than depend on projectiles. The 'sit back and arrows+boomerang+bomb' strategy is a good one and a fun one to get skilled at, but it cannot be the only way you know to use Toon Link. If it is, then many players will know how to deal with you, counterpick stages, and choose different characters against you.
I'm talking to all toon link players here - try some matches without using projectiles at all, and figure out ways to use the rest of TLink's kit until you don't feel disadvantaged against certain characters anymore.