The problem is your attitude to our answers. When we answered your question honestly with the only possible answer you replied with snark. What did you expect that would cause? You want to learn to deal with projectiles, then learn to powershield. If everyone has told you this all over smashboards it's because it's the best way. Asking in more boards won't give you a different answer when there is only one right answer. Learn to power shield. Go into training mode with a friend or with two controllers, Pick Any character and Falco/Mario. Stand them close to one another and either ask your friend to only shoot laser/fireball, or set the PC to do it, or press B with your toe on that controller. Then, with your char, try to power shield that projectile. Do this over and over until you can power shield it most if not every time. Now change it so that you're approaching as you need to powershield. First walking, then running. Voila, in a couple of days you'll be able to power shield. Dot he same for teching. Dot he same for rolls, trying to ifnd the moment when you can punish them.
Was this what you were looking for? See, there are no free wins, nobody gets good or improves due to some magical advice. You need to work on it, practice. There's a reason we have a Link's Training grounds stage. If you don't work, you'll never rise above mediocre. Also, focus on one char. Many people do what you do; they come in here asking for advice but never say which char they main. We can't give you solid advise unless we know your main because every char plays different. That's why Mus are a ting and are so important.
As you can see, your original post was aggressive and condescending. On top of t hat, it asked a trite question in a poor way. We replied with the only right answer and got snark back, and attitude. How on earth do you expect people to react? Cower? As Zelkam said, you show respect, you'll get respect. We go by Newton's third law of motion here.