That's a bit generalistic though.
Sure, don't do that if you had a messy break up, still harbor romantic feelings for them, or any other background of negativity.
But if I amicably broke up with my (non-existent) ex, and he asked for a good weeknight dinner recipe, or wanted to know the brand of hair product I'm using, sure I would respond.
Truth. I still send and receive texts like “happy birthday” from certain exes. A couple we may even occasional text each other if we see a show or movie or something the other likes, or there is a crazy deal on something we know they’d like. There’s a balance- and I mean- hopefully a current partner is secure enough- but even then being “too close” to your ex can cause problems for current or future relationships- or even for you or your ex. There are exes I stopped texting simply because it as clear (and in one case confirmed) they still had feelings. So it can be crueler sometimes to stay in touch than to cut them lose so they can heal and get over you. It’s... it’s all circumstantial. Between the exes and their partners and all the other complexities of dating.
But- if you don’t know yourself, or know yourself well enough to know contact with an ex will hurt or possibly lead you to a mistake with them, or vice versa- then yeah. Maybe just don’t text them at all.
Sure, don't do that if you had a messy break up, still harbor romantic feelings for them, or any other background of negativity.
But if I amicably broke up with my (non-existent) ex, and he asked for a good weeknight dinner recipe, or wanted to know the brand of hair product I'm using, sure I would respond.