Interesting topic, first of all we have seen both 10k and 14k in 2019, that tells me that the price has come up alot since we saw 3k and there is still interest.
Depending what you describe as mainstream but i dont think 2017 was mainstream, for me mainstream is when Bitcoin/Cryptocurrencies is alot more known and used. Today we dont have that and cant see it either, partly because we cant send transactions fast enough.
One very big problem in 2017 was slow transaction speeds and high fees, if you reed around the internet you see alot of threads/discussions talking about this problem. Today its probably a bit faster but not that much, this would mean that 20k today with the same bullrun would cause the same problem, so you could argue that we cant see 20k today because we havent fixed the problem we had 2017.
Another big problem was exchanges, in 2017 the exchanges couldnt handle the traffic, this became a big problem, today we have stronger exchanges with alot better servers and staff, however the transaction speed and cost is still a problem. We also have alot of problems with exchanges get hacked, Decentralized exchanges is also something we need.
Can we see a new ATH? Yes, but probably not today and if we would see a new ATH anytime soon there is a big chance we see a crash as well, however with the upcoming halving no one knows where the price can go.
I think we nee to see a good scaling solution, maybe Lightning Network, which by the way have made big improvments this year. We have also seen alot of companies beginning to research blockchain and we have much more interest in the blockchain today compared to just a few years ago. I could say we have made alot of ATH in blockchain space but not in price
2017 was a interesting year but also a very dangerous time, alot of new people entered crypto with the minset buy now before it is too late when in fact it was already too late to invest. Now alot of peolpe are just waiting to get out. Crypto is not always a price but have usecases.
Just my thoughts.