I think you refer to the wiki entry on game clones here: Video game clone - Wikipedia
The rationale for refusal differs between different patent systems in different countries, but patents are generally NOT possible for game mechanics. As a general rule, patents will only be granted for technical innovations of various types. Under UK law, for example, software-related patents are usually only granted if they cause a useful technical effect outside the computer which the software is running on (process control type inventions), or result in an improvement in the computer architecture (as opposed to specific programs running on it). On the other hand, things like image processing software has been found patentable in Europe at least, and there is an interesting case where a patent was granted for software that designed drill bits, so there’s some grey areas so long as you’re dealing with essentially technical subject-matter. The situation has been tightened up a lot in the US - the law is still a bit nebulous, but the USPTO is doing all it can to avoid granting ‘soft’ software patents.
Generally speaking, copyright applies to the expression of ideas, not the ideas themselves. So a 3rd person camera system is not covered (and also not original - another requirement for copyright), nor a battle system and so on.
HOWEVER a portion of text (e.g. a potion name) may be protected by copyright, if it is original, and may also in extreme cases be covered by trade mark law (I’m pretty sure a ‘Zelda/Mario/etc power-up potion’ may cause problems in theory). To infringe copyright, you have to take a substantial part (at least, that’s the position in the UK, likely similar elsewhere), so it becomes an issue for the lawyers - so play safe if you can because no-one wants the lawyers to get involved…
(Edited to add: there are some unusual and somewhat inconsistent cases where computer game patents HAVE been granted in Europe (and the US), including a way of indicating where a football pass is going, highlighting a target in a race game, and so on. To be safe, do a quick search for a particular feature or for a particular applicant, but it’s effectively impossible to search every aspect of a game.)