First of all, who decides what are the “rules” of what makes a “true” DJ? I personally don’t subscribe to that.
So you can stop worrying what other thinks before thinking of yourself as a true DJ.
Secondly, imho, if you have software that you like and that fits your workflow, you don’t need to learn any other software.
There is quite a lot of work that goes into getting to know your software intimately enough and in making your collection ready in that software (cue points, beatgrid, etx.). And most of that information is not tranferable to other software. It can’t hurt from a hobby point of view to have a quick toy around with other software, but there is, again imho, no reason to do this to become a true DJ.
If you are a CDJ-DJ, it helps to be able to play on various brands and models. At the end of the day, those pieces of gear are pretty much all the same in essence, so a short learning curve. But if you are a digital DJ, you bring YOUR laptop, with YOUR software, you don’t show up somewhere and start using whatever computer and whatever software they have ready for you.
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