My general attitude is that I'm all for reboots of a property that has really cool or fun ideas but the original version never really lives up to the full potential of what it created or, even worse, completely wasted what it had and turned out pretty bad as a whole. I was never a huge fan of the Scooby-Doo franchise, but it does have some fun characters and themes, so I have no problem with it constantly being rebooted, especially since I'm getting through Mystery Incorporated right now and I'm liking what I'm watching. It might even succeed Zombie Island as my favorite Scooby-Doo thing, and Zombie Island was also the beginning of an attempt to reboot the franchise.
I also enjoyed the She-Ra reboot as its own thing even though I care very little for the original She-Ra series. I had no fears of them "ruining the original" because I don't really think the original was all that great (or even good) to begin with.
I'm even welcome to reboots of things that were generally good, but may have completely dropped the ball with its ending. I'm actually not too upset with how the original Full Metal Alchemist anime ended (though I would have to rewatch it to say for sure, because I really don't remember how well everything tied together) but it does seem generally accepted that the reboot Brotherhood turned out better. I, as well as a number of other fans, would also enjoy a TV reboot of A Song of Ice and Fire once the books are completed since Game of Thrones has infamously botched the ending (arguably the last few seasons as a whole).
Regarding spiritual successors, at the end of it, I don't think they really offer the same thing a reboot does, so it's hard for me to compare them. I don't have any specific examples in mind, but I feel like the best spiritual successors aren't intentionally being so, but their creators were so strongly inspired by their predecessor(s) that it's clear what they were but we still receive an original idea that can stand on its own. On the other hand, some spiritual successors may try to intentionally draw parallels to their inspiration and get so caught up in reminding its audience of something that they already enjoy that the work just comes off as a shallow imitation of a better idea. In those cases, like with an inferior reboot of an already good existing product, why not just watch/read the original?