I don’t have trouble with most blu-rays, but there are a few I have not been able to get to rip. This includes, brand new, out of the box blu-rays. I have not tried any ultra-hd blu-rays yet, even though my external blu-ray drive should support it.
I do recommend looking at the makemkv forums for blu-ray drives. Some of the cheaper external drives do not last very long! A higher quality internal drive with an external case works much better. There are some people on the makemkv forums you can buy from. They have specific drives they like and they’ll pre-flash libredrive firmware on them.
I also prefer ripping to downloading. I am quite specific about how I like my movies ripped, and like to keep embedded subtitles, extra languages, full DTS surround, and commentary tracks, which are often missing in downloads. It does take a bit more time, but I also find I am way more careful about curating my collection and keeping it high quality.