If you're reading marketing ads for supplements, they'll focus on some aspect that sounds desirable: boosts this, blocks that, makes you younger, etc, mostly based on bad science. As Shanti1 says, they have plenty of other, less fabulous for marketing, purposes in the body. Our cells evolved to use various nutrients and expect them in various amounts. Varying too far from the optimum amounts of those nutrients will likely result in less than optimum cell functions.
From my own experience, I can say that the different fatty acids do/have affected my ME symptoms. There was a period where palmitic acid made my symptoms worse, unless I added extra carnitine. Conjugated linoleic acid temporarily blocked my sensitivity to proline. At present, adding cis-linoleic acid improves my sleep patterns. I expect that many other people have similar responses to specific fatty acids.
This applies to amino acids too. For whatever reason, I've become sensitive to proline, which is a non-essential AA abundant in most foods. There are far too many reactions in the body using proline for me to figure out just how it's doing what it's doing. It doesn't even need to be an actual chemical reaction; a proline (or any other) molecule might just interfere with some other molecular reaction, like a stick jamming a machine. Minimizing my proline intake is worthwhile for me.
The important thing for PWME is to figure out which nutrients have a noticeable effect on their symptoms. We're all different, so we each have to experiment on ourselves. If omega-3 supplements provide you with a noticeable benefit, continue taking it. If it doesn't help, try something else. If it doesn't provide a benefit, but also not a detriment, and you've been convinced that the possible long-term benefits are worth the expense, that's your choice to make. I've definitely benefited from various supplements at various times, so I think it's worth the effort of trying things and paying attention to effects. The ones that didn't help, I didn't bother continuing to take.