No, His quote from Exodus was proof that they were alive then and are still alive. Just because you and the Sadducees can't see them doesn't mean they are not alive. The after life includes all the time after we put off this body of flesh.
The problem with your statement is that Jesus said he was proving the resurrection of the dead, not a ghostly state of existence before the resurrection. That's a stubborn fact you've been unable to get around.
Just as Paul says, to be absent from the body, and present with the Lord.
Which is also perfectly compatible with the biblical statements that the dead have no being, thoughts, or knowledge even that they are dead. One event is a
prerequisite before the second may be accomplished, that is a list of a sequence, not an equivalence.
And Paul told how he had seen a vision...which was the risen Lord. Are you claiming visions are figments of someone's imagination rather than a being from the spiritual realm? Are you denying Paul saw the Risen Lord and referred to Him as a VISION?
First, a heavenly (legitimate) dream or vision is not a figment of one's own imagination, though I allow that a false vision could simply be imagination. From here on I will simply say "vision" and assume you know I am speaking of a
legitimate vision.
Second, the conveyance of visions are well known for containing symbolic or metaphorical elements that can be misunderstood. When God speaks plainly in a vision, those are words that we can trust. But when God has other elements within the vision, those are seldom literal and sometimes defy immediate interpretation.
Do I need to bring up some examples to demonstrate this? Pharaoh's vision of the thin kine and the fat kine? (Genesis 41) Nebuchadnezzar's vision of the statue with the head of gold and feet of mixed of iron and clay? (Daniel 2). Peter's vision of the unclean animals in the sheet? (Acts 10). John's vision of four horsemen and beasts and dragons with seven heads and a woman in the wilderness? (Revelation).
Notice how angels are called "visions". Don't you believe in angels?
Luke 24:23 And when they found not his body, they came, saying, that they had also seen a vision of angels, which said that he was alive.
Granted that the word "vision" can also mean "appearance. But in most of the biblical cases visions are in the form of dreams containing images. Even if a vision contains images of angels, this would not require actual angels to participate. God can create visions without requiring live actors.
If you deny the existence of Moses and Elijah on the Mount, then you must deny the existence of the Lord (vision) and angels (visions). You can't pick and choose.
I can say that the disciples that were with Jesus that day saw a vision that contained elements that represented Moses and Elijah. This is stated in the gospel, just as surely as Jesus explained that what his disciples was a vision. Clearly they didn't understand the meaning of the vision, as their initial suggestion was that they should build three tabernacles.
Besides this, your suggestion that this vision of Elijah was the real Elijah is countered by Christ's own explanation just a few verses later in Matthew:
Matthew 17:9-13 KJV
(9) And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead.
(10) And his disciples asked him, saying,
Why then say the scribes that Elias must first come?
(11) And Jesus answered and said unto them,
Elias truly shall first come, and restore all things.
(12) But I say unto you,
That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them.
(13)
Then the disciples understood that he spake unto them of John the Baptist.
If they had actually seen Elijah (not merely a symbolic element of vision) then doesn't this answer seem a little strange? Shouldn't he have said, "Elias has come already, did you not see clearly with your own eyes?" rather than telling them that John the Baptist was the fulfillment of the saying that Elias would first come before the Messiah?
Not only that, but when they were told that it was a vision, why would the disciples have asked "Why then say the scribes that Elias must first come" if they understood that the "vision' was real and Elias had just come?
Clearly they understood that they hadn't seen the REAL Elijah or else they wouldn't have asked that question.