I prefer to trade mostly BTC-based pairs as well since my only goal's just to accumulate and more Bitcoin, so just trading through BTC pairs eliminates any fees I might have to pay to convert USDT or USDC or any other stablecoin back into Bitcoin. I still do trade with leverage on sites like Bitmex for pairs such as BTCUSD simply because I've got good experience with that specific pair and I know how things go with it, but typically I do still trade most altcoins against BTC.

There's still plenty of opportunities everywhere, however. Find what you like and stick with it, because anything can become viable if you start looking at it the right way.