Something is off here - but what?

Say I'm going through the struggle of not having enough exposure from my newsletter.

Would it be fair to say that I'll search google for "newsletters on [similar topic]"? Then if I don't find them that way, maybe I'll search google for "newsletter cross promotion" and come to your site.

If that's the lead-up to coming to your site, let's look at how the site will fair using the Forces of Progress, the back-and-forth forces in the mind of the visitor:

1. The "Struggle" force of "I'm not getting enough exposure" is not a hard hard struggle. The person won't be driven by desperation to the point of begging other newsletters to feature their own. So already, the driving momentum getting a person on your site isn't super strong. It's also not zero. So many products are just clever tools that don't address a hard struggle and because of that will never work. But yours addresses a real annoyance. However, because it's not that strong you'll have to make up for it with the next two forces.
2. The "Attraction" force is one of the ones you can control. One of the ways to do that is to reflect back the struggle to the visitor, so the visitor can feel like they've been "understood". Another way would be to paint a picture of what your product/service will do to make the connection with other newsletter owners happen (heighten trust that you'll deliver on the promise).
3. The "Anxieties" force is pushing the visitor away, putting the brakes on the momentum. The price is usually thought of as the biggest anxiety, but a lack of price is almost just as anxiety-inducing. In your case, not having a price, that's a big point of cynicism (what's this all about?). The other anxiety about your offering is that I don't know what I'm getting into if I join. Will my personal information be harvested? Do they even have any names yet? Will this take months before there's a directory of enough newsletters? Is the author doing the pairing manually? You can explain all this with honesty, and that will help reduce the anxiety. The answers might push some people away, but maybe some people will join by way of reciprocation (the author was open, I'll be open). See what I mean? Tend to the anxieties. Because if the anxieties are stronger than the Struggle Force and the Attraction Force, you can be sure the next force will be a real challenge.
4. The "Habits" force is the gravity well pulling back towards "Not this, not now". It's all of the "I'll just" statements in the mind of the buyer. "I'll just contact some newsletter owners myself." "I'll just hang out in similar communities for a while until I find fellow newsletter authors". That force points to the real competition for your product. That's the bad news. The good news is that you can actually help your visitors with those "I'll just" alternatives right from your site, creating more trust. "Don't want to give away your information just yet? Here's a guide on how to.... Here's a list of communities you can try to hang out in...." By doing this, normally after your pitch, at the bottom of your page, you'll provide value to the visitors who were about to leave anyway and therefore create a secondary relationship with them. You might get some word of mouth from that gesture. They were never going to sign up to your main thing (the Habits force is strong!), but maybe the secondary offering might help them on their way just enough, and spread the good will.

So that's my advice. You got something that addresses a struggle. The page could be improved to make sure the first two forces clear the second two.

Hope that helps.

I get what cross-promotion is, but it's a vague term. I think that's the problem.

It's not clear what exactly you're offering.

When I read your H1 ("Newsletter Cross-Promotion Made Simple"), I instinctively think, "Okay, so you help me promote my newsletter across different platforms, like social media, news sites, mobile apps, RSS, etc. etc., helping me to gain subscribers," but then the H2 ("Connect to hundreds of other newsletter creators") confuses me.

Then again, I don't have a newsletter, so maybe it will make sense to someone with a newsletter to promote.

hi @whereismypen I took a glance at your landing page while I was doing my weekly landing page feedback live-stream today, I tried to give you some honest feedback and I've highlighted a few areas of improvement. I also took some time to do the timestamps in the video description, so it's easy to find! Check it out: https://youtu.be/SxyVsA58c34

what sort of questions?

is this a 2 sided promise? how do I know the promise is kept? are all of the promotions affiliate offer style, meaning I at least get paid for doing my side, if it becomes one sided?..

What about "Find similar newsletters in your market that you can partner with"

Maybe add small screenshots/images of what your product does, images convey what the website does faster than text