Forbes is right in saying that "this rally is much more sustainable than 2017"?
In my eyes the 2017 rally, which actually started in 2015, was very sustainable, it lasted for more than 2 years and brought the price from $200 to nearly $20,000, and even after the crash, the price was still tremendously higher than where it was at the begging. If this rally would be as "sustainable" as the 2015-2017 rally, we could look at reliable $60-80k price ranges in a few years.
It's only from the perspective of people who entered close to the ATH that rally wasn't sustainable.
There are different ways of looking in to it. By mid-2015, the exchange rates had hit rock bottom at around $200 per coin. This represented 85% decline from the ATH levels of 2013 December. Then there was a small recovery, and the prices reached $900 per coin by 2017 January (which was still 20% lower than the 2013 ATH level). I would rather consider
the movement from 2015 to 2017 January as a "recovery", rather than a "rally". IMO, the rally started in Q1 2017 and lasted for less than 12 months.
I think by "2017 rally" they, Forbes, mean a shorter period of time, starting mid September 2017. That's when Bitcoin really really jumped big, from $3,600 to $19,000 three months later. And the current rally has started in the end of September 2020, with BTC at around $11k, and if it is indeed a more more sustainable one, we can expect Bitcoin going over $60k in 2-3 months from now.