I have recently observed no matter how good your TA is, it doesn't always work on alt cos most alt price direction is impacted by BTC price.
Doing TA with altcoins is not good especially if they are very new altcoins or with low trading volume. They can be easily manipulated by insider trading activities too that you will not see with Bitcoin because it is old enough, no big free float, and with high trading volume, it's hard to do insider trading with Bitcoin.
When BTC is up all other coin move up. So why spending time on doing technical analysis on alts when doing it on BTC gives you a potential clue of most assets price direction?
It's not true that when Bitcoin is up, all other coins will move up. Price movements of altcoins don't always follow Bitcoin movement because the market is zero sum and capital must be in one asset like Bitcoin before it moves to other coins. Before people taking profit in Bitcoin and move their capital to altcoins, altcoins will not move up.
If capital in Bitcoin stays the same, not move, you will need new capital flow from outsiders to move altcoins up.