For some people, who may wish to upgrade to a better Ryzen CPU later, yes, it makes sense. For others, it may not, if performance NOW and spending less NOW is more important. Fact is, the 2600k outperforms the Ryzen 3 CPUs. You'd need a Ryzen 5 1500x or higher to outperform the 2600k.
Even then, the single core performance of the 2600k is STILL better than that, or ANY Ryzen CPU. So any game or application that favors strong single core performance is going to perform better with a 2600k than with any Ryzen CPU. If it even marginally uses more than 8 threads OR if you are doing any heavy multitasking that might require or benefit from additional cores or threads, such as simultaneously running recording software, encoding, streaming, many browser tabs, etc., then the 2600k will start to fall behind.
Obviously though, there is no upgrade path from the 2600k so unless you are certain you are not going to need anything more than what you get as is from that CPU, it makes little sense to buy one, new or used. It's money better put towards something with a future in it.