I know that altcoins seasons too will surely come, but the majority of the altcoins if care is not taken would have already lost all their pride and lost all their customer to bitcoin, if they are not even lost finally themselves, but i trust more in those coins that are at the top market in either exchanges or the top in the most popular ranking site of coinmarketcap, then bitcoin dominance would have reduced a little bit or remain constant for a while.
We have still been in the early days of altcoin season, which is certainly not a season for all altcoins. I strongly believe that most of altcoins born in 2017 and 2018 have been death and nearly unable to recover. Their are some main internal factors for their failures, not come from general market conditions. Their developers are inactive or already abandoned their projects. In some projects, there are no proofs that their developers abandoned but inactively conditions are surely not good things.
I believe in this year and next one or two years, there is very difficult to catch capital from investors if one project only claims, I will use source code, fork from this one, and build up my strong project, blah blah.
CEO of Binance has same opinion about it. He said, in crypto market, there are only chances left for ones that have real usecases.