As a rule, I'm a terrible texter on purpose. People know I'm horrible at it, so they don't get offended when I don't reply.
It's not that I don't care or that I intend to disrespect the person I'm not responding to, it's just that I hate being so accessible at all hours of the day. I have responsibilities. I have a job. I have other people I live and work with. But most of all, it's hard enough for me to manage my highly distracted personality without people texting me stupid emoticons and buzzfeed pictures every six friggin' seconds.
That and I personally prefer in-person or on-on-the-phone interaction. When I'm there with someone, I'm there with someone. I'm not juggling my focus between fifteen billion different other things. Because god knows, as soon as you respond to a text, there's a 90% chance of having to have a back and forth conversation about virtually nothing because the other person KNOWS you see it and you don't want them to feel like you're giving them the brush off.
And that's not even the worst of it. Once you're done with one person, another person texts you five minutes later and before you know it, you've got nothing done and a whole bunch of pointless interactions that could have been more meaningfully communicated in person or over the phone. Suddenly, when you go home at the end of the work day, instead of spending time with your loved one, you're beating yourself up over how unproductive you were during the day because as soon as you were in the zone, somebody interrupted you with gif of a tap-dancing alligator in a top hat, #zomgyougottaseethis
If your ex shared any of my views, give him a break. It's not that he didn't care or wasn't thinking about you. He was probably just trying to retain his sanity and focus on what was in front of him at the time. Not everyone is wired to be thinking about their loved ones every five minutes.. and even if they are, they prefer to get stuff done at the office so they can go home and enjoy their company, guilt-free.