Do you know what would be stupid?
If there was completely different ships between the prequels and the original trilogy. It was bad enough that the prequels had nothing that was seen in the OT, 20 years is not long enough for all the ships to disappear.
If somehow in the middle there were ships that were completely different and not inspired from existing star wars ships i would be really annoyed.
I strongly disagree with you and its one of the things that largely annoyed me about the prequels.
The F-16 has been a thing for over 40 years. That's in the real world where there have been rapid advances in technology.
Star Wars tech is more like a meta shift than actual advancement. New things are not necessarily more advanced than the old they are just better tailored to the needs of the moment. It shouldn't be unusual for Clone Wars military tech (and their variants) to still be in use (and possibly still in production) during the period of time that TFA is set.