What are the demands and disadvantages of Christianity?

What Jesus Christ did was to offer everyone (who wanted it) the possibility of resurrected eternal life in Heaven. 

Such was the Simple Positive Good News... Albeit this seems very quickly to have become hedged about with negations and threats, and distorted in many ways... 

Such as the idea that the system of salvation was one of tests, presided over by a divine judge, and conducted like a legal trial. 

And demands for obedient submission to this-world persons and institutions who claimed to control  access to Heaven. 

And the threat of everlasting deliberate ultimate torture (i.e. the novel invention of "Hell") for those who failed the tests, refused obedience, and did not qualify-for Heaven.

Such is human nature when offered simple positive good news; the message swiftly gets complexified, distorted: recast into the already-existing shapes of this mortal life and world.  

But, even setting aside such worldly intrusions and distortions; Christianity is still not the best of news for everybody; because there are both demands and there are disadvantages to accepting Jesus's offer of salvation.

Although available to any who desires it; salvation is not for everybody; because not everybody desires it as first priority; and for many possible reasons. 

Including that:  

1. Many or most people would prefer an ideal, perfect (or at least much better) life in this world and before death; and this is their actual life-priority. 

This could be for many possible reasons, including that they believe that this mortal life is all that is real.  

And, after all; everybody has some tendency (perhaps overwhelming) towards seeking to optimize the "certainties" of short-termism, above prioritizing the contingencies of the long-term. 

Yet (leaving aside the satisfactions of this temporary mortal life) there are plenty of people who express complete uninterest in even the question of their own post-mortality, and total indifference to the nature of their condition and situation after death. Clearly, such people will ignore Jesus's offer of salvation as irrelevant. 

2. Some people do not wish to be resurrected after death. 

Because they would prefer something else to happen. Maybe some type of reincarnation, or to become a pure spirit - perhaps living is a continual state of bliss? Or perhaps they would prefer annihilation - whether total destruction of the self, or dissolution of self-awareness.  

3. Not everybody agrees with Jesus that love is, and ought to be, the primary value of creation. 

And probably this is the main reason for refusing Jesus's offer of resurrection into a Heaven rooted in love. 

People often prefer... something else... Such as maximizing their own pleasure, power, status. 

For them; a paradise of ecstasy, prestige and total domination; is much more appealing, than attainment of what Jesus made possible.  

Others are focused on the primacy of a negation towards specific entities. For example it appears that plenty of people are mostly concerned with destruction of some person, group, place; or some other revenge against these. Perhaps there is a dominating desire actively to inflict torment on somebody or something.

(Ultimately, perhaps; there is the rejection of God's whole project of divine creation - a preference for chaos over creation.)

In a nutshell; there are multiple types of reason why Jesus's offer of salvation is not of interest to many (most?) people. 

And this despite that salvation is available to everybody who wants it; the fact is that lots of people do Not want it. 

They prefer... something else; and that remains the case even when threats of punishment and torture for disobedience - whether in this-world, or the next - are factored-out.