Whether it's a LinkedIn message or they somehow they got my email, with one exception, I never respond to recruiters. Their emails could be polite, personal, and non-aggressive. Or they could still have template placeholders (ie. "{{their name here}}") and tell me in my first year as a developer that I'm a great fit for a senior engineering role. I just don't respond, because otherwise it'd be hours/week of sending email.
Even if I had a template to respond with, it still would take up time. It's strange to get so many emails from people and never to respond, but to be fair, it's the equivalent of cold calling. Do you guys just ignore it too?