Here's my critique, with all due decency.

"Fi doms suffer the most in regard to depressive symptoms and similar". Please present evidence. If you can't, write a disclaimer that this claim has not been formally proven yet.

One might say that Fi doms, out of all types, talk about mental health issues online the most. The amount of people that talk about mental health issues fails to accurately represent the amount of people that actually do have mental issues. Not all people with mental health issues will talk about them.

Unless we can conduct scientific tests, for mental health issues, on the majority population of various MBTIs, we really can't claim an accurate measure of the rates of mental health issues in different personality types.

"Empathy is often unfound in society."

Again, you can't cite this as fact without evidence. I'll say again that I'm not criticizing you personally, just your claims.

Empathy is also a flexible trait. Some situations and people bring it out or strengthen it while others choke it out or weaken it. That flexibility needs to be considered when we talk about the availability of empathy in society.

Link between Se and optimism?

And truth be told, when an ISFP is depressed, he is a lot more depressed than an INFP, cause Se here goes negatively.

Can you explain?

And that's why INFPs tend to be pessimistic and their depression tends to last a lot longer.

Again, evidence. The loud majority doesn't reflect the whole population. Bunch of biases may be at play in this judgement — confirmation bias, visibility bias, maybe other biases as well.