Of course not. But the limited selection of alternatives certainly adds to the pain of switching platforms. Therefore it's not so simple to "just buy another phone".
That's not the accusation. The accusation is that disallowing sideloading and forcing all customers to observe a single philosophy is especially big of a risk to the user considering that there's little competition. The fix isn't for Apple to create better competition, it's to allow sideloading. I am not saying it's their "fault" for having a lack of competition, that is just a reality of the market they are in.
