My family is from a Buddhist majority country, and most of the people of my ethnicity are Buddhist. I've studied quite a bit of Buddhism and spoken to many monks, whom were really interested in speaking with me, and actually I've had much more interesting conversations with them than any priest.
First there are two books that are pretty good to check out about Buddhism:
This one speaks of a person's journey from Tibetan Buddhism to Catholicism
http://www.ahandfulofleaves.org/documents/Unexpected%20Way_On%20Converting%20from%20Buddhism%20to%20Catholicism_Williams_2002.pdf
This one (also available online) shows a western person who became a monk and realized how broken the whole system is, and how ineffective Buddhism seems. He indeed praises the work of nuns doing charity, and notices in Buddhist majority countries, the minority Catholic population is responsible for majority of charity, and even sees the nuns progressing spiritually more through their work.
https://www.goodreads.com/book/show/33796532-the-broken-buddha
Now to the main issues:
#1 Karma is victim blaming. According to canonical scriptures (Tipitaka), anything good or bad that happens to you is because of previous actions. If you are beautiful in this life, it's because you did something good in a previous life, and if you are ugly, because you did something bad. Same with being rich, being successful, being poor etc. Buddhism claims to "remove the caste system", but that is only true in a specific sense - in the sense that one from any birth can decide to become a monk. It doesn't eliminate that if you are born in a wealthy family, it means you have done some great merit in a previous life and so on. As such, you will see in buddhist majority countries, marriage proposals heavily consider the birth of the family and all sorts of other things. Jesus replies about the blind man from birth, that it was not because of his sin, but only that the works of God to be displayed on him. If you've ever been in a bad situation, suffering horribly, also thinking that you deserve this for something you've done bad is just ridiculous and abhorrent to most people. The little child that was repeatedly molested by their parents - that child had done negative things in their past lives and got what was deserving to them. Kim Kardashian and Paris Hilton being rich and popular, it's because they were very good and pious people in their previous lives.
2. Re-birth/Re-incarnation: Again according to canonical scriptures, the Buddha says that we have had uncountable past lives. He refuses to talk of the creation of the the universe, saying it's not conducive towards liberation, but also in one place in the Pali Canon he does provide some sort of creation type story. Regardless, many times it's said that we all have innumerable past lives. However in order to add some sort of urgency to it, it's said that to have a birth in an age where the teachings of a Buddha is accessible is very rare, perhaps once every 1000 births, and so we shouldn't waste this opportunity. Now to someone this might give you some sense of urgency - to anyone who doesn't know about mathematics. It has and can be proven for example, that there are *equal* number of even numbers vs natural numbers. There are also *equal* numbers of numbers divisible by 5 as natural numbers, or numbers only divisible by 1 million. If indeed we have innumerable past lives, then even if we only encountered the teachings of a Buddha once every 1 billion lives, we would be encountering them the same number of times as if it was every life. It's hard to grasp if you don't know math, but this is definitely true.
Regardless another way of looking at it is that there is truly no urgency in Buddhism. Your current life is no more important than the billions and billions, and literally uncountable other lives you've had. Each life becomes virtually insignificant, since the number of lives we've lived is claimed to be infinite. We can keep going back and find more lives apparently, it never ends. Other than just making your life insignificant, it adds a lot of complacency to life.
In buddhist majority countries, the majority of laypeople don't think of being liberated in this life at all. All they are concerned about is doing "meritable actions" that will secure them a better next life, and so on, until they can possibly one day be liberated. You don't even really need to care about liberation, since the promise is that things like wealth, beauty etc, will all be secured for you in a better life. Now this might sound alright, until you realize what the best action that a Buddhist can do is.