This is an objection to Marketing Automation that I can completely understand and if all you are looking for is a lead generation tool, then possibly marketing automation is not right for you at this time.
Data capture is a big part of what Marketing Automation can add to your business. Through utilising landing pages and forms on your website this is a great way to gain visibility of WHO those unknown visitors to your website are. Yes not every person is going to fill out a form when they are on your website but you are still gaining more information than you were before as once they fill in that form and provide you with their name and email address, that is when they become tagged and you can see their digital behaviour with you.
The value it brings to the people that are already in your database is not through gaining their contact details, but through tagging them and being able to see what they viewed on your website previously, in their current visit and whenever they return. Imagine the value that would bring you, being able to see what everyone in your database is looking at on your website?
Therefore this is where the value is for those prospects that you already have the contact information for, if you data base size is 50 thousand email addresses, how valuable would it be if you could see what those fifty thousand people are looking at and therefore being able to tell when they are ready to buy.