You ask for a name when someone signs up to your email list, but you never send an email that is addressed personally?
It's super easy to just add "Hi {first.name}" to the top of your email to make your contact feel that the email is for them, not just generic.
Yes most people understand the idea of mail merge and know you didn't personally write and send the email, but not making this basic effort makes you look like you don't care.
It's like you introduce yourself to someone new and don't take the time to remember your name. Every time they communicate with you, they say hey you or don't even acknowledge you; they just start talking.
Treat your email communication like a conversation; if you have someone's name in your list, use it.