So far and based on The Dead Sea Scrolls website " Many biblical manuscripts closely resemble the Masoretic Text, the accepted text of the Hebrew Bible from the second half of the first millennium ce until today. ".
Some manuscripts don't, and resemble the Septuagint more closely, some resemble neither textual tradition. There were multiple textual traditions of the OT back in the days (an opinion anathema among both the Jews and the Protestants), some (most) of which have been lost, which differed from eachother on some points. The Masoretic text simply reflects the textual tradition closest to rabbinical theology, having been assembled and redacted by them in the 10th century, acutely aware of the challenges posed by Christianity (and, to a much smaller degree, Islam).
The Septuagint, having been assembled in the 3rd century BC, - more than a millenium before the Masoretic text - having been used by Hellenic Judaism (Philo of Alexandria, e.a.) and Christianity (the Apostles, the Church Fathers, e.a.), and without having been influenced by the differences between Judaism and Christianity and thus being a neutral arbiter of sorts, shouldn't be thrown away too rashly. Even Protestant translators tend to clarify obscure Greek passages by using the Septuagint as a referrence and early witness.
Yet even then most messianic prophecies haven't been expunged from the MT.