You are unable to look at the OT without the influence of the NT. You see everything through Paul-colored glasses, so you cannot see what Jesus' followers saw.
That’s funny because all I did was refer you to the Old Testament book of Isaiah. But, as to your “argument” suggesting that using New Testament “voices” such as Paul (a self-proclaimed “Pharisee of the Pharisees) somehow colors looking at Christ with some sort of bias is absurd. All the New Testament converts (Jesus’s followers) had to go on were the OT scriptures. So looking at what they had to go on (the Old Testament) was enough to convince them of Christ’s claims, His offices, etc. And, I guess His resurrection might have also influenced their considerations somewhat, as well.
These early Christians were all Jews and weren’t looking at Christ to prove the scriptures but in looking at the scriptures they proved Christ.
But, of course, Christ had to deal with objections such as yours in the days of His flesh:
John 5:38 And ye have not his word abiding in you: for whom he hath sent, him ye believe not.
John 5:39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
When are YOU finally going to give US the CORRECT answer; Teacher?