Canon means nothing. They had Scripture, and it was called Scripture, at the time of the apostles. Paul's writings were called Scripture by Peter and there was the entire OT.
There are plenty of other doctrines that the Catholic church adheres to that are not any more explicitly spelled out in Scripture than sola Scriptura so that argument against it is not a valid one. It cannot be applied in a case by case basis. If a doctrine like the Trinity can be established by proof texts, so can sola Scriptura.
That same Roman Church recognized very early that when Christians interpret scripture without any authority then what you get is a “my interpretation is as good as yours” result.
The Catholic church is not unified in doctrine. There are significant differences of opinion between the Orthodox and the Roman rite. Not to mention the number of other Catholic rites which exist.
Also, one must recognize that the Roman Church is almost 2K years old and comprises 1/6 of humanity. You have to ask yourself, would our Lord allow 1/6 of humanity to pursue a falsehood in His name? Not likely.
Might doesn't make right.
It's a meaningless argument to make a claim of being right on.
Anyone who accepts Jesus and believes in The Trinity is not the enemy to another Christian, in my opinion.
Anyone does that IS a Christian.
We must be united in purpose, not necessarily denominational affiliation.
With out proof this is at best conjecture.