Remember that I’m defending a fairly moderate view of sola scriptura, according to which it is a norm. It should be used to test what we believe and do. But Christ left the keys to the Church. As I understand it, for Jews this is the power to interpret Torah, so it leaves us with the responsibility for interpreting and applying Scripture.
At to justification, look at Jesus’ practice. He uses Scripture, which he often called the law and the prophets, quite regularly in conflict with the Pharisees. In particular he used it to judge their traditions.
But there’s another issue. We claim to be followers of Jesus. How can we not want to base our faith on what he taught and did? Scripture is our only primary source for that. For the first few decades of the Church, there were people living who remembered him. But today, Scripture is the only significant source.
That’s not to devalue Christian experience, and all the thinking that has gone on since. But still, we should give precedence to Jesus’ own message and actions.