Your above points are right but the last part is not correct as merits are not distributed randomly to anyone and those who are lucky will get them.If your posts are of good quality and have some useful information for the reader's you will definitely receive merit for them.You might not get them on spot or immediately after posting but can get them some time after when high rank members noticed them.

But if you think your post are good but not merited report them in Report unmerited good posts to merit sources and if they find it suitable you will get the same.

But don't think merits are given or distributed on luck based factors but completely dependent on what you are posting and your knowledge which is reflected in your post quality.Work hard for them and you will get them.