Are you really a new player or did you have your sibling play your account when you started?
https://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/3263464914/2377007056833504?tab=overview
almost 10 cs per minute on the very first game
https://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/3263466126/2377007056833504?tab=overview
https://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/3263447687/2377007056833504?tab=overview
10+ cs per minute on the 3rd and 4th games is not something a real newbie can achieve (hell, I don't think half the player base can achieve it), not even in co-op vs AI. If you did have your sibling played on your account, then he or she royally screwed up your account because the system detected that you are not a noob so it puts you against other highly skilled or smurfs for the rest of your low level account. I looked at your match history and your cs-ing skill scream smurf or shared account.
If you are a smurf, then you really can't complain being put against other smurfs or high skilled players. If you are a true newbie, then I suggest you create a new account and don't let anyone else play on it.
Why can’t I just be inexperienced without being flamed to hell for it?
But your account is not deemed "inexperienced" because either you are a smurf or your sibling played on it and screwed its status.
Do experienced players really have such fragile egos? Is this what I can expect from the game moving forward?
Yes, because your current account is marked as a smurf and will almost always get matched with other smurfs that usually include toxic banned players. The fault lies partially with whoever played on your account (or if you are a smurf).