Looking at the 3-Day chart of the Bitcoin Dominance ratio spanning from the altcoin season of 2017 to now, it looks like history could repeat itself for a 2021 altcoin season.
The ratio topped out at 72.04% back in Sept. 6th, 2019 and then retested that same level and couldn't break through it at the end of 2020 going into 2021. From here, the dominance has done nothing but drop like a falling knife. For the past 2 months, Bitcoin Dominance has been steadily falling without anyone paying much notice.
The momentum is falling and I think the dominance is on the path to hit the 53 - 58% zone. If the Dominance doesn't hold at 53% we could see another altcoin season 2021 all the way down to the 35 - 40% zone.
With all the NFT hype its possible this could be a first catalyst or a catalyst that pushes the real start of altcoin season.