Because it might not have been the “Spanish”, but certain people who ruined history. So it’s not fair to blame a whole country for the actions of a few.
It's pretty fair to blame the entire social and political system of 16th century Spain, which at that time was centered on religious persecution, mass murder, large-scale theft and exploitation, and quasi-slavery, leading to centuries of profoundly racist tyranny in the Americas. The book-burning cultural genocide was just the cherry on top.
(As is common for feudal occupiers of foreign lands, and by no means unique to Spain) the worst kinds of psychopaths were continually elevated to positions of authority and then granted almost complete impunity to do what they wanted, with an ideology that treated the recipients of their exploitation as sub-human.
The initial conquests and the immediate atrocities that followed them (arguably the worst period) were mainly quasi private enterprises. The state even tried to reign them in to some extent due to significant social/religious pressure at home. Of course that was largely superficial and hardly enforced after boatloads of silver and gold started arriving.
The priests and missionaries that followed them were likely the group that was most sympathetic to the natives (of course only in relative terms compared to the "conquistadors" which is a very low standard).
You're literally applying birth sin for it to make sense, because none of the Spanish people alive today had anything to do with it
Even worse, what hnidiots3 was trying to convey: 99% of the population that were alive during the time period you'd have described as "Spaniards" were entirely uninvolved in these actions, and wouldn't have supported them either, likely.
While the Mayan culture was literally doing human sacrifices - the average person living in Spain wasn't inherently evil and wanting to cause suffering to other people. Despite their culture being kinda shit.
They just wanted to live their live, which was mostly being a farmer and working.
Are you saying that the average person in Spain did not support colonialism (let's suppose after the benefits of colonialism became apparent)? Would they be horrified that Spaniards had killed "barbarians" and "savages" (as they were described) and gained great riches? Other people have brought up religion; how many Christians condemned the Crusades?
How specifically do you think the average Spaniard benefited by the crown building a colony?
Do you think the crown then went and splurged on their farmers, reducing their taxes or something? Because no, that didn't happen.
The benefits for this was entirely with the aristocracy and wealthy, not with the average Spaniards.
Going by some of the statements in this thread, if Spain-after-colonialism becomes richer and more developed, such that the average citizen's standard of living increases, then colonialism benefitted the average citizen. Benefit to the colonized peoples aside, surely many other people benefitted, even if they weren't immensely enriched.