It is a common description of RDA that “capitalization doesn’t matter”, but that’s not exactly the case. RDA has extensive rules for capitalization of elements, detailed in Appendix A.
For example, RDA A.4 (covering titles of manifestations) says to generally capitalize the first word of a title, and to capitalize other words in the title according to A.10 – A.55 as applicable to the language involved; those guidelines basically match The Chicago Manual of Style, so many words we think of as “proper nouns/names” (people’s names, corporate bodies, months, etc.) should be capitalized.
Appendix A does include an optional alternative to create an in-house style manual and follow that instead of what is in the appendix, but the LC-PCC PS encourages catalogers to follow the appendix (though it permits “take what you see”), and the NLA PS says to follow the appendix.