There's a huge problem there.
All who promote that "this generation" was in the first century always avoid the fact that the generation to see all those events would also see the actual second coming and gathering of the saints.
Mat 24:4 And Jesus answered and said unto them, Take heed that no man deceive you.
Mat 24:5 For many shall come in my name, saying, I am Christ; and shall deceive many.
Mat 24:6 And ye shall hear of wars and rumours of wars: see that ye be not troubled: for all these things must come to pass, but the end is not yet.
Mat 24:7 For nation shall rise against nation, and kingdom against kingdom: and there shall be famines, and pestilences, and earthquakes, in divers places.
Mat 24:8 All these are the beginning of sorrows.
Mat 24:9 Then shall they deliver you up to be afflicted, and shall kill you: and ye shall be hated of all nations for my name's sake.
Mat 24:10 And then shall many be offended, and shall betray one another, and shall hate one another.
Mat 24:11 And many false prophets shall rise, and shall deceive many.
Mat 24:12 And because iniquity shall abound, the love of many shall wax cold.
Mat 24:13 But he that shall endure unto the end, the same shall be saved.
Mat 24:14 And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
Mat 24:15 When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand
Mat 24:16 Then let them which be in Judaea flee into the mountains:
Mat 24:17 Let him which is on the housetop not come down to take any thing out of his house:
Mat 24:18 Neither let him which is in the field return back to take his clothes.
Mat 24:19 And woe unto them that are with child, and to them that give suck in those days!
Mat 24:20 But pray ye that your flight be not in the winter, neither on the sabbath day:
Mat 24:21 For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
Mat 24:22 And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened.
Mat 24:23 Then if any man shall say unto you, Lo, here is Christ, or there; believe it not.
Mat 24:24 For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
Mat 24:25 Behold, I have told you before.
Mat 24:26 Wherefore if they shall say unto you, Behold, he is in the desert; go not forth: behold, he is in the secret chambers; believe it not.
Mat 24:27 For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be.
Mat 24:28 For wheresoever the carcase is, there will the eagles be gathered together.
Mat 24:29
Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken:
Immediately after the tribulation will the sun and moon go dark and the stars will fall from heaven, all being global events. Did that happen after the Roman's destroyed the city and temple? No.
Mat 24:30
And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory.
All the tribes of the Earth mourning and seeing Christ coming from heaven to the Earth. Again, a global event. Did that happen in Ad70? No.
Mat 24:31
And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.
The gathering of the elect by angels in Ad70? No. The disciples would have been the elect of their generation and they certainly weren't gathered by angels. This is the same event known as the Rapture but it didn't happen in Ad70 and hasn't happened yet.
Mat 24:32 Now learn a parable of the fig tree; When his branch is yet tender, and putteth forth leaves, ye know that summer is nigh:
Mat 24:33 So likewise ye, when ye shall see all these things, know that it is near, even at the doors.
Mat 24:34 Verily I say unto you, This generation shall not pass,
till all these things be fulfilled.
"all these things" includes verses 29-31 which shows the second coming and the gathering of the saints. Other scriptures tell us this timeframe is also the time when the dead in Christ are resurrected. Did any of those things take place in Ad70? No.
None of those things happened in the lives of the disciples proving he was NOT talking about their generation not passing before "all these things" occurred.