I've seen over one dozen websites believing that BTC will skyrocket in the upcoming years.
The platform I use is Coinbase.
I'm thinking of just buying BTC-USD and just leaving it be.
Any thoughts on this strategy?
Buying BTC-USD using the dollar cost averaging method is still very relevant to do, but don't let BTC be stored on the buying and selling platform.
Whatever platform you are going to use to buy Bitcoins and choose to just leave it on the buying and selling platform without moving it to a trusted wallet, then that is not a positive strategy but a strategy of handing over the safe keys to robbers to take your money.
BTC USD? Is this some kind of a peg in order to prevent the value of BTC to fluctuate? But I thought OP only wants BTC alone and not other variations with it. That will still work and it was in fact better because there is no risk on it, I mean the coin is originally developed by Satoshi and we are sure that he won't do some manipulations or sabotage it like any other coins out there.
Coinbase is a registered company. It's not new anymore so I don't wonder on why the OP and others are confident on leaving their funds on them for a long time but as you said, it is still better to transfer the coin to the wallet which lets us own our keys because we still don't know what can happen to them later on. It's better to be safe than sorry.