But Christianity didn't borrow from the past? There seems to be varied opinions as to this.
Of course it borrowed many things from the past, but that doesn't mean it wasn't also revolutionary in certain areas.
it just tends to tell me that religions are rather natural and something to be expected, but not necessarily true and without some rather large complications.
Are any ideologies true or without large complications?
I suppose the former (of course), since what we have today (in striving for various freedoms and in our scientific understanding) was always there to be discovered. I can't really imagine an alternative universe where non-truth was what ruled. And for myself, I do tend to see religions holding back scientific progress although I know there are different viewpoints on this and contributions made.
It's based on an assumption that what we value now has always been valued, and what is useful now has always been useful.
Humans would always invent technologies, but the vast majority of societies in human history have seen no need to invest scarce resources in learning 'pointless' scientific knowledge. Why would they? Experimental science was ridiculed at first and only gained popular legitimacy due to links to theology.
In the west there were numerous factors that contributed to the development of science, and many of them were directly assisted by religion/religious institutions:
Mass education (not directly vocational) - church schools and universities
Mass translation of foreign texts - the church
Willingness to invest scarce resources in 'pointless' science and social prestige for doing so - supporting theology
Belief the universe is ordered along rational principles that can be understood - creation
Belief in a progressive body of knowledge that can be added to - regain knowledge lost during 'the fall of man'
Educated people with free time and access to scientific literature - friars and clergy (who contributed disproportionately to such progress)
Funding for research - the church
etc.
Given these things were very rare across human societies, the probability is against an alternative, religion-free history of the west seeing modern science developing there. It's possible of course, but you aren't likely to be dealt 2 straight flushes in a row at poker.
This is true, but in the past has anything else been so potent?
Religion has both driven change/progress and resisted them. I'm not sure it is particularly potent at resisting change
in general.
Of course it has been at times, but all cultures are resistant to change at times.
One man's suicide bomber is another man's executioner - as in, all the religious executions because of heresy, blasphemy, etc. Any difference?
While even 1 is too many, religious executions really weren't that common. Even the big bad Spanish Inquisition 'only' killed a few dozen a year on average. And, AFAIK, no one has ever been executed for promoting scientific theories, other than Galileo it's hard to even name another scientist who was persecuted at all.
20th C totalitarian regimes on the other hand likely executed far more people for 'heresy' than all religions combined, and persecuted more scientists.