Replace transmission fluid in 2009 Hyundai Accent or no?

In recent oil change, mechanic said to change tranny fluid as it getting dirty but that it wasn't urgent to replace, can still keep going for a bit.

I had wanted to get it changed that same day, but no time from mechanics at shop so I would have to go back another day and haven't gone back yet.

For whatever reason, I was researching online and found mentions of times where it may be better not to replace tranny fluid even though old as it has worn down well with the transmission & swapping it with new fluid makes it a different environment and could cause problems instead. And it applied to new and/or old cars, I forget exactly.

So for this particular car, should I change the fluid or not? It's at close to 30,000 miles. When I checked it, it didn't look pitch black dirty, but then again I'm not a mechanic to know exact dirty level coloring.

I don't think car's had tranny fluid changed since bought from dealer, so it's been a few years now.