It just different tools it's all art. (for reference I used to do both traditional and digital art, though my arthritis has made it so I no longer can do traditional art so I stick to pretty much digital now)
I wouldn't say that digital artists being bad at traditional (which is a rather questionable statement and dependent on what part of drawing you are talking about) and vice versa isn't as large an issue as people seem to think it is when it actually does happen. As you can say the same about switching from different traditional mediums in art. If your good at acrylic painting that doesn't mean you'll automatically be good at watercolour painting as well by default. Though some skills and use are universal between the two there are still a lot that aren't, they're different sets of tools with different ways and requirements and methods to using them. And that example is still within the painting medium, markers, pencil crayons, graphite, pastels, charcoal there are so many different mediums and they don't all work the same. You need to learn how to work with them to properly take advantage of what you're capable of doing with them.
When I first started digital art, honestly the hardest thing for me was colouring, it's just very different from how I would colour in pretty much any traditional medium I was versed in using. It took a while to get used to but that was the same for any new art tool or medium I was learning how to use. You need to learn how to and take the time to learn get it to work for you, it's never going to be automatic just because I know how to use another art tool or medium.
As for the differences, the largest differences between the two for me are these things, and none of these things really have a direct affect on the quality you are able to produce.
Digital is much cheaper over all, EVEN if you invest in a cintiq or high cost drawing programs. It's still cheaper than the accumulated cost of traditional art tools and supplies.
Clean up after using your tools is practically not a thing.
Maintenance and care for longevity of your tools is also a million times easier and less time consuming.
No mater what method on the computer you are using to colour or ink you don't have to worry about fumes.... holy crap some of those paints, glues and markers (just to name a few) can get harsh I tell you man...
Digital also requires a heck of a lot less space in your house, both for storage, work set up, and storing your finished results.
And these are the most notable differences between the mediums I notice, the only one that could directly affect your art being cost, (because sometimes you don't have the money to justify the price tag to get that shade, colour or hue of paint/marker/whatever that you know would work best but can't get, so you have to do a work around to work with what you have or do without it) Aside from that. It's just different tools. Just like any art tool it's gonna require different method and skill set to use, you just need to learn how to use the tool.