In my view, there are 2 main reasons for that, fundamental ones.
First, exchanges manipulate prices like crazy. You can see it on new listings, on old coins, just everywhere. They’ve learned how to earn money directly from their users deposits. As soon as they did, we’ve seen a massive price drop of alts in 2018. And we continue to see it right now. If you think that it’s impossible for exchange to suppress price of low cap coin, then you have to check FRM for example. They’ve had 200k usd initial mcap. And it was suppressed even with such a low mcap. How? Cause most users transferred their coins on one exchange to never withdraw it again. In such case exchange can continuously dump users tokens on the heads of those who buy more and not transfer those tokens out from exchange. Such manipulation obviously comes with a high risk, especially on a low cap coin, where every once in a while a rather big investor finds out about the project and try to make a withdraw. And exchange in this case have to stop withdrawals/deposits. Cause they simply doesn’t have enough coins to make a payment. In other case, exchange “got hacked”.
Second, users hold most their coins on exchanges. And those who doesn’t, usually hold them for a long time without trying to buy/sell. Such behavior on users side, make it possible for exchanges to have a full control over the price and let them easily earn from dumping price.

If you interested how exactly exchanges do that. They just consider users tokens/coins as their own. Use them as a leverage. Sell let’s say at 1usd and quickly dump it to no less than 50% of its price. If person see less than 50% price drop, with enough liquidity, he’ll consider cutting the loss. With more than 50% price drop, person consider to hold until recovery. The lower the price, the less people consider cutting the loss. At 90% drop almost no one really cares about cutting the loss anymore and just hold infinitely.
So it dropped 40%. People start selling massively. Exchange buy back from those people and now they just earned 0.4usd from every token they’ve leveraged at 1usd. Now they can repeat this scheme taking 0.6usd price as a basis.
And they can repeat this thing indefinitely, until someone try to make a big withdrawal in the wrong moment. If there are many such clients at once, exchange stops withdrawals/deposits. Until they’ll purchase tokens somewhere else.

What can you do to change that? Just never hold your tokens on any exchange. And use exchanges only when you really have to buy more/sell the pump. The sooner more people realize that, the sooner market starts recovery.