The problem with Altcoins is the dynamics of the cryptocurrency market today. When Bitcoin rose rapidly, Altcoins fell as capital cycled back to BTC. If BTC goes down, altcoins fall together, putting them in a precarious position.
Basically, the key to the Altseason is the easing of the Bitcoin rally to give the market a chance to grow as that is where aggregate market volume is likely to spread again.
However, December or January 2021 will probably be the Altseason.
A strong sign of the Altseason can also be seen from the ongoing consolidation of the Bitcoin rally in the ETH / BTC pair, where these two cryptos are still the largest in the crypto market so that the sentiment from the technical side can be a strong psychological market reference for the potential Altseason.
The fact that if bitcoin goes up a lot, the btc/alt pair goes down is the main reason, you are right about that, but if we could have bitcoin increase a lot, like how its high right now, and stay there, while money goes into alts, that btc/alt pair will go up, and since bitcoin is already a high price, that altcoin price will increase even more.
We have seen many many altcoins that increased in fiat price for example while going down in bitcoin price, why? Because, if bitcoin goes from 10k to 50k and a coin goes from 10 dollars to 20 dollars, that altcoin made 2x profit while still lost in btc/alt pair anyway because btc went up even more. That is why some people stop caring about btc/alt pairs and only care about alt/usd because they want to make fiat profit, and yes bitcoin may have made more, but some of those people wanted to make money no matter how much.