Are people who say “not my problem” delusional?

It depends on context .It can be aversion if they felt the problem was hard to solve ,or maybe they had another more important problem that would've cause them more suffering if not tackled first or there maybe a valid reason,if they where blamed for not doing work, when it wasn't assigned to them in the first place then "its not my problem" ,would be a valid reply clearing out a misunderstanding.In most cases they felt attacked when asked why didn't you do this or that & had hard time seeing dependent origination .So its better to ask the question in another way .Do you know why did that happen ?,or simply stating the problem and its effects.

So from the reply you can clear out the context.

Equanimity is one of the four brahmaviharas.

I once read -- though I no longer remember where -- a suggestion that one might be an antidote to an excess of another.

For example, equanimity is good, but too much isn't good, and should by counter-balanced by or mixed with another like compassion.

Similarly compassion is good, but too much isn't -- e.g. if you can help someone then help them, if you think you can't help, or perhaps if you try to help but don't seem able to, then practice equanimity.

Householder Dweezahr, interested,

first helping oneself to increase and gain, renew refuge and gratitude toward real helpers who owe all credits here:

- Namo tassa bhagavato arahato sammā-sambuddhassa -

yes, helping oneself in wrong ways or refuse to help someone else if able is grave delusion, yet total common in this world of people heading downwardly in high speed.

"help your self first" is what everybody would hear since child very often in Buddhist countries, yet not so many understand what it means to help oneself first.

What ever conductive for happiness in this world, the next and beyond, has/had giving as it's cause. Starting from material, to time, skills, not harming... virtue and all ones bad desires.

So it's very importand to focus on ones own happiness in right way and a person open to give what ever he/she can is a person headed toward prosperty, longlife, honour, happiness and power.

Knowing this the wise seeks after what ever good possibility to make merits.

So when the world is on fire with aging and death, one should salvage [one's wealth] by giving: what's given is well salvaged.

What's given bears fruit as pleasure. What isn't given does not: thieves take it away, or kings; it gets burnt by fire or lost.

— SN 1.41

Understanding that right, that the usual investments in what is regarded as own, is just food for the flames, one understands this warning rightly, since just kammas effects will stay yours till the point of liberation, awakening, is reached:

"Monks, these two are fools. Which two? The one who takes up a burden that hasn't fallen to him, and the one who doesn't take up a burden that has. These two are fools."

Fools, when seeing a burden, or asked to give, say off good cause: "not my problem" (and not seldom argue such with misinterpretation of the teachers advices)

Having followed from the raw giving material things, to giving happiness and freedom of fear by ones keeping of precepts, one will sooner or later surely arrive at the point where the most refined, of which needs to be given any, comes as ones last burden, having fallen to one: the five clinging aggregates, which are the root reason hindrence from liberation and becoming one who is really able to give and help: another Bhagavato, real liberal.

So it is good if you, being touched by it and able to understand, don't waist even more time in invest of what is already lost and focus on helping your self first.

(Note that this gift of Dhamma is not dedicated for trade, exchange, stacks or entertainment but as a means to make merits toward release from this wheel)