That study seems odd for a variety of reasons. The only affirmation used was ‘I am a lovable person’, and rating happiness was determined by how they answered a question on relationships.
Either way, the study did find that those with high self esteem got a boost from the affirmations. So claiming the study finds affirmations harmful isn’t really true, since people who actually believed it and repeated it did better than those with high self esteem who didn’t. So affirmations did have an effect, just not the desired effect in those with low self esteem.
If cognitive dissonance and maintaining the integrity of the self are the factors then a study on low self esteem people with a different affirmation may find different results. Affirmations like ‘all humans are worthy of basic levels of kindness and love despite their failings and mistakes’ might have gotten a different result since that is more in line with what a person with low self esttem would probably already think and would not be seen of as much of a threat, but which could slowly change a person’s psychological integrity.
Looking up on wikipedia, there are some studies which show self affirmations which are considered valid by the user make them less defensive when presented with unhappy news.
So what happens if people with low self esteem perform affirmations they actually believe before doing the ones they do not believe? Do the ones they believe make them less resistant to the ones they do not believe?
Also the article speculates that the individual is cementing their worldview as someone with low self esteem. Seeing how the study was done once with no follow up (as far as I can see) I don’t see how you can make that argument. All in all it is an article with an agenda that doesn’t go in depth enough to throw out an entire aspect of psychology.
As far as are they seriously trying to help? I’d say yeah most are. Either way, self affirmations are a small part of self help. I have no idea how effective self help is, but I would assume most people do it because they found something that works for them and they believe it works for others too. Whether that is the case or not though, who knows.
FWIW your OP seems to be confirmation bias of your pre-existing beliefs. Go stand in front of a mirror and say “self help is a tool selfless people use to help people help themselves” for 10 minutes and give us the results on your mood. Are you more depressed or less?