How can I repeat a button press every X seconds in a web browser using automator or another tool?

I want to have the computer simply press space every X seconds about 5000 times. I thought automator would be straight forward to do this but I'm shocked to find thousands of options for all kinds of complicated and obscure things but not simple straight forward "record and repeat these button presses". Am I missing it somewhere?

I literally just want to repeatedly press one button with a single web browser tab open about 5000 times with some delay. Why is this so hard?