An
excellent question indeed.
All JMO:
First, lets consider that seastars, in particular Linckia and Protoreaster (aka Chocolate chip stars) are under intense collecting pressure from not only this hobby, but from the souvenir trade. Actually, you can add the sand sifter star Archaster to that list as well. Even worse, in both of these "hobbies' the star is more desirable when "perfect" meaning all arms are the same length....which could mean, in some respects, that the mature adult "brood stock" is selectively being removed.
Let us also consider the dismal survival rate of the majority of these stars. This is not a question of "it has worked for me for x amount of time (often measured in months - far too short to know true success). This is a question of overall survival rate in this hobby.
And for many stars, this is a very very low rate long term (beyond 18 months).
Now consider that scientists are debating whether seastars actually show any signs of old age in the wild. Too many feel "oh it is short lived anyway" or "oh it was killed by something" when these are both not true. The majority of seastars that make it in to this hobby live extremely reduced lives in our tanks. Many take months and months to starve to death. (I am making the distinction here, as it should be, between seastars and brittlestars, which are very different beasts).
So it comes down to the research you've done, and the tank you can provide. It seems quite clear, that success with stars like Linckia and Fromia is highly correlated with tank size (and more directly amount of LR). It is, IMO, irresponsible to buy an animal when you do not have what is considered to be the minimum requirement to keep it. There are exceptions, sometimes it works...but if you are counting on it to work, then I think that is an issue.
I personally feel that Protoreaster, being a predatory star, has more likelihood of success long term, though require a diversity of foods (including algae, BTW).
Archaster, the sand sifter, in smaller tanks - this case without a lot of surface area of sand - tends to do very very poorly.
I think it is critical that people research stars. I think it is critical that they provide the minimum care recommended, including parameters and acclimation. I think it is critical that they encourage others to approach their decisions conservatively - not necessarily "it worked for me" but more "it doesn't work for most." If you do these things, then consider a star.
But if I could personally arrange a ban of certain animals in this trade, some of the first on that list would be certain seastars.