It will surely show more bloody market when BTC will rise up more since a lot of investor will sell their altcoin which is really the way to accumulate more bitcoin. And this might happen more when halving is near.
And i can see that only few altcoin can follow up when bitcoin pumps up and that's why we need to be always ready for what will happen in the future.
good and growing altcoin is also quite a lot that can be relied on, although I agree with what you say that the influence of the movement of bitcoin will make altcoin very directly affected. there is altcoin that will be affected badly and there is altcoin which actually enjoys bitcoin rising. because they can already manage and the movement is pretty good.