What does "sorry I suck at texting" mean?

I've had two girls send this to me. Both times it was like, we texted for a little bit, then she didn't respond. Then the next day or later that night she says "sorry I suck at texting".

I know it does not literally mean they suck at texting, it's obviously an excuse for not responding. Could it be that the conversation was boring or something? Is this a bad thing or just neutral?
What does "sorry I suck at texting" mean?
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