There are some things to consider when deciding if it's 'wise'. Number one, older powerful cards tend to use A LOT of power. This is fine if you already have the power supply that can handle it. If you have to buy a new power supply though, that undercuts the advantage of saving money when buying a used card. The other big thing is the question of whether your system can make use of the extra power. In your example, if your CPU is already maxed out with a 1050 Ti, then using a 290x gains you nothing.
There are other things, like the older cards generating more heat and noise, but that isn't such a big deal. Some people just care about performance.