I think one of the reasons why Bitcoin trading is the best and the best is that when one trades only Bitcoin, his profit will be less than other coins or tokens and vice versa the chances of losing from other coins or tokens will be much less. I personally think that Bitcoin can be the only product for long-term trade management or long-term planning.
Do you think there could be anything other than Bitcoin in terms of long-term planning?
There is no other pair other than USDT may be considering its stability point of view. If you think that trading alts with other alts is beneficial then that thought is not wrong as well. The reason is simple: as long as you are able to trade against other pairs with good volume and your orders are getting fulfilled then you are already doing great.
The only concern is volume and not the price. For any trading pair with only slightest accuracy prices are one and the same. Otherwise we would have been doing scrapping and leaving the trading behind us.
Most of the time bitcoin is good due to it's volume, and little hiked price. But as such I don't think it matters a lot?