They probably aren't. But that isn't incompatible with both them desiring to continue to live and them contributing to whatever society they are reborn in to. After all, people today are primarily concerned with their own lives first and foremost, yet we manage to work together to build societies just the same.
>why do we imagine that someone from the present would be more effective at using those tools than someone from the future?
Diversity of thought. That doesn't mean that revived-person-x is going to be better at any particular productive activity than someone who was born in to the future in question. But simply by being from a different era, I like to think that there is potential to be able to contribute meaningful value. Or, put another way, while it is true that the world benefits greatly from those who are the best of the best, it is also true that there is a place for a large number of competent but not exceptional people to do the bulk of the work, and that their lives have positive value, too.
(It seems silly, leaving aside the ethics of it, that we may find ourselves in the position of wishing we had the "diversity of thought" of peoples that we had long since either wiped out or pushed to assimilate into what's rapidly becoming a single global dominant culture.)
I mean, it rather sounds like we have changed the pitch from "If you desire, you can avoid death" (and the specific form of "If you have a terminal disease at a young age, we can freeze you until the disease can be cured, so you can live out the rest of your life") to "It is good for society that we build mechanisms to clone large numbers of people from the past into the present to lead average lives," which at the very least is a whole different ethics ballgame.
For one, there's the question of what happens if turns out that we can clone people from the past, en masse, even without them having been prepared specially. (Perhaps certain types of embalming cause enough stability in brain structure. Perhaps we can revive people who froze to death, like the hundreds on Mount Everest or similar mountains.) Going back to the idea that we only need a partial restoration and that there's no magical "self," is it ethical to clone them, if it is helpful to present society? Is it ethical to clone parts of them, if that's a technology we develop and it's beneficial?
Also, it seems pretty unlikely that humankind is on its path to having a vastly lower population than we do today, and we have yet to be assured that we will be able to colonize other planets. Lives have value, but when we have reached the capacity of Earth, how do we weight the potential value of cloning millions of people rom the past?
You could also imagine that, in a future where we are close to being able to revive human brains, we can just query human brains via simulation without bringing them back to life. The ethics of that are different, but - at least with consent from the person while they were be alive - it doesn't seem obviously wrong.
Re work improving the world - why do we imagine that someone from the present would be more effective at using those tools than someone from the future? Again, take the example of Arthur: if he returned, what would he do? What would you have him do? Or if even Isaac Newton were to return, would he be able to keep up with the brightest minds of the present generation of students who all took calculus in high school? I'm not doubting that he'd still be a sharp thinker, but would he be doing anything groundbreaking and world-changing like he did in his natural life, or would he "just" interview well at FAANG?
I'm not disputing that both of them would do things beyond their own wildest dreams during their lifetimes. Honestly, I think Arthur would have a lot of fun being in the House of Lords (which is probably where they'd put him) and Newton would get a blast out of being an entry-level engineer at FAANG. I'm disputing that they would do anything beyond what the natural-born of today would do, and that unless you have a sentimental correlation between your revived self and your old self, there's not really a point in one more average or even above-average person existing in the future.