I won't say I never make trade routes, but they are rarely a major source of income. Mainly I use them for maintaining relations - and when a war breaks those routes, it's almost never worth making them with someone else. I don't think I've seen a game where my trade income exceeded 15% of my tax income - and my tax revenue will generally run my empire with a huge surplus by itself.

Of course, this will vary wildly based on your preferred map size, difficulty, planet count, civ count, etc. But for a gigantic map, abundant all, it is very possible. Certainly possible up to crippling/masochistic difficulty, anyway.

Most cases I don't develop trade routes, and there are games I even have tech trading off to fully isolate myself and others. It can be done, it just really makes you watch your purse-strings.