The question is why all the previous generations are not judged for their part in killing the prophets and why all the wrath falls on the last OT generation. Certainly Jesus' generation had far less excuse for rejecting God than former generations, seeing, as they did, the miracles of Jesus and the testimony of John the Baptist but why did every previous generation get exempted? Also we know that every person will be judged, but is there also a communal or generational judgment as well?
1st: I don't see any mention of prior generations being exempted from judgment.
Maybe the AMP version will be an easier read then the NIV you posted from. (I prefer KJ & am not promoting or knocking any versions)
luke 11:
45 One of the lawyers [an expert in the Mosaic Law] answered Him, “Teacher, by saying this, You insult us too!”
46 But He said, “Woe to you lawyers as well, because you weigh men down with burdens [man-made rules, unreasonable requirements] which are hard to bear, and you yourselves will not even touch the burdens with one of your fingers [to lighten the load].
47 Woe to you! For you repair or build [o]tombs for the prophets, and it was your fathers who killed them.
48 So you are witnesses and approve the deeds of your fathers, because they [actually] killed them, and you repair or build their tombs.
49 For this reason also the wisdom of God said [in the Scriptures], ‘I will send them prophets and apostles, some of whom they will put to death and some they will persecute,
50 so that charges may be brought against this generation [holding them responsible] for the blood of all the prophets shed since the foundation of the world,
51 from the blood of Abel to the blood of Zechariah [the priest], who was murdered between the altar and the house of God. Yes, I tell you, charges will be brought against this generation.’
52 Woe to you lawyers, because you have taken away the key to knowledge (scriptural truth). You yourselves did not enter, and you held back those who were entering [by your flawed interpretation of God’s word and your man-made tradition].”
53 When He left there, the scribes and the Pharisees began to be very hostile [toward Him] and to interrogate Him on many subjects, 54 plotting against Him to catch Him in something He might say.
Additional notes that may be helpful:
Gen 15:16 But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.
(NOTE: Amorite insight:
https://www.gotquestions.org/Amorites.html
Romans 3:25 Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
(NOTE: Vines definition, "forbearance" a holding back, a delay of punishment, Romans 2:4; Romans 3:25)
In my view a more crucial truth in Jesus teaching here begins in Lk 11:15-20. With their all out rejection of the Holy Spirit & therefore the promised Kingdom Jesus taught was upon them. I.E. judgment passed & the begining of their end.