What am i doing wrong with my cold emails?

Hey guys. I run a design and development agency. I've been cold-mailing for a week now.

I'm sure 90% of the problem is with my template:

Hey [client_name],

We came across your website. Not sure if you know, but we strategically design websites that drive revenue.

We noticed your website could be improved. Without a new design, you might be losing a lot of potential clients.

Just wanted to send you a message and see if you might be interested in checking this out.
If so, let me know, and we can set up a quick call!

Have a great day.

[my_name]
[agency_website]

I use Apollo to search for emails. And later mail them in a style similar to the above.

I'll be grateful for any suggestions. Thanks. Have a great day.