Agree, you should be looking to your son rather dil. He's rude if he is happy to let you watch his child weekly, but doesn't bother to even reply to your messages. I'd be pulling him up on that.
I feel like it's really common for mother-in-laws to label the dil as the 'boss' or 'in charge', when actually the husband / son has often forced them into that role because they're too lazy to facilitate relations with his own family.
Your dil probably goes to see her family more because she puts the effort in to maintain a relationship with them. They are her family. Your son has exactly the same options and opportunity to do the same with his family, but he's choosing not to. That's not her fault or her job.
Look, you're very generous helping them with childcare weekly and I don't want to disregard that. But if you're feeling unappreciated, that's really on your son and you need to communicate that with him. You don't have to guilt him, just tell him what you want eg I'd appreciate it if your could reply to my messages. I'd like to see you, can you tell me what works for you so we can make it happen.
Also, just an fyi, your dil knows that you only think she's 'ok' and that you perceive her to be the 'boss' over your poor hen pecked son. She knows and that will be why she's resistant. She'll naturally gravitate to people who think more of her.
I say this as a dil who knows my mil thinks similar of me. She's never explicitly said it, but I know all the same. My family however think I'm lovely and easy going and don't think I'm an overbearing boss boots who orders my dh about (because I'm not!). So guess who I want to spend more time with?