I have been living off my affiliate income for more than a decade now. And I have been contacted by people wanting me to promote their products / services 2-3 times per day for the past 10 years. I have seen a lot of emails and a lot of products. 99% of them I rejected or ignored.
The main mistake people do is that they don't realize that an affiliate with established traffic and income doesn't have any incentive in promoting your new, unproven item, unless you make a very good impression, unless you pay them more than the others and your page looks professional and cookie duration worthwhile.
More experienced affiliates have had cases of clients not paying commissions and doing dishonest stuff, so we tend to be very suspicious.
I see a lot of genius guys on ProductHunt, very smart makers and creators, with unbelievable skills, who create amazing things that I wouldn't know how to create, but whose strategy is basically to just be launching here and hoping for the best. I think this is gambling. Some people were able to do that easily about 10 years ago when there was no competition.
In my opinion, right now the people who have the luxury to simply "launch" are twitter influencers with a big following. They will post a tweet, get buyers and traction. But what's working is not their product, but the audience they already have.
I am by no means the most expert business owner out there, but in my experience the best chance of success for your apps are:
1) If you're a twitter influencer developer, who can simply post and immediately get hundreds of early adopters that will help you get the word out.
2) If you have money to pay for ads, like Twitter ads for example.
3) If you get randomly viral.
4) If you painstakingly look for affiliates to promote your product.
I can help you with 4) so I created Affiliate Hunter.