There hasn't really been any bull market in altcoins since 2014 (except for Ethereum).
Seriously?
How about Monero which got 20x pump a while back?
How about NEM, which got 20x too a few months ago, or SC which used to be 7 sats in January and got 170 sats a while back?
How about NAUT, STEEM, ETC, SYS, SDC, ...?
I love bitcoin, but honestly, how long does it take for you to get even a 2x profit in bitcoin land?
Good investment in altcoins does that much much faster.
What is true however is that for every altcoin increasing in value, there is another falling. The only trend of the altcoin market is what share altcoins have compared to BTC. That is currently at 83.6%:
You can always make profit if you pick exactly the alts that go up while avoiding the alts that go down. Very similar to the stock market, but hard to achieve.