Good question, needs a reply.
The biggest problem I have with dispensationalism is its ahistorical approach to Biblical exegesis.
Before the 1830s, did anyone teach a pre-tribulation rapture? There were many in the early church who held to premillenialism, but not a pre-trib rapture.
According to the various historical creeds there was a belief in the second coming to raise and judge the "quick and the dead" followed by eternity in heaven or hell. I don't think "the tribulation" was a specific event before that coming. Theology has developed since the Reformation with various interpretations of prophecy.
What did Jesus himself teach about the tribulation?
Mat. 24, Mark 13 & Luke 21. Jesus' prophecy begins with the destruction, continues with various occurrences which are NOT signs which will take place before "this generation" has passed. Clearly within about 40 years.
These events also include the tribulation that occurred before the destruction - that the believers were warned to flee the city to escape when they saw the signs.
Some of these events are extraordinary, including Jesus "coming in the clouds" so that many details of the prophecy are taken as referring to the second coming rather than the destruction. We need to consider the "Partial Preterist" interpretation which sees two comings, one veiled by clouds, for the prophesied destruction in AD 70, and the final coming for resurrection and judgment.
Mark 13:28 “Now learn this parable from the fig tree: When its branch has already become tender, and puts forth leaves, you know that summer is near. 29 So you also, when you see these things happening, know that it is near—at the doors! 30 Assuredly, I say to you, this generation will by no means pass away till all these things take place.
31 Heaven and earth will pass away, but My words will by no means pass away. 32 “But of that day and hour no one knows, not even the angels in heaven, nor the Son, but only the Father. 33 Take heed, watch and pray; for you do not know when the time is.
Jesus taught that "the tribulation" would occur before the AD 70 destruction. The would be no specific signs before his final coming. We are in the situation now.
Take heed, watch and pray; for you do not know when the time is.
The traditional timetable is that the tribulation happens first and then the rapture. How can we be spiritually prepared for the coming tribulation if we needlessly expect that we're just going to be raptured anyway before anything bad happens?
Exactly! The generation that rejected its Messiah had all the warnings, and all the Gospel preaching from John the baptist, Jesus & then the Apostles from Pentecost onwards. And those who rejected both warnings and Gospel suffered the tribulation and Jesus coming in clouds for destruction.
See how "clouds" are used for invading armies in the prophets.
Jer 4:13 - Behold, he shall come up as clouds, and his chariots shall be as a whirlwind: his horses are swifter than eagles. Woe unto us! for we are spoiled.
Of special interest is Jesus' quotation of Dan, 7:13 to his accusers, which clearly refers to his ascension.
I saw in the night visions, and, behold, one like the Son of man came with the clouds of heaven, and came to the Ancient of days, and they brought him near before him.
Mar 14:62 - And Jesus said, I am: and ye shall see the Son of man sitting on the right hand of power, and coming in the clouds of heaven.
Peter preaches Jesus' ascension, Stephen sees the ascended Jesus -
55 But he, being full of the Holy Spirit, gazed into heaven and saw the glory of God, and Jesus standing at the right hand of God, 56 and said, “Look! I see the heavens opened and the Son of Man standing at the right hand of God!”
The unbelieving, rebellious Jews would "see" Jesus coming in the clouds, fully vindicated.
Secondly, do dispensationalists honestly believe that unbelieving Jews don't need to receive Christ to be saved, because they belong to a previous dispensation? What Biblical evidence is there for that?
I can't answer that, except to note their full support for the the people who control the modern state of Israel in its war of hatred and destruction against the Palestinian people.