Kovid said something very interesting a long while ago, on one of the other various threads that this subject crops up on from time to time. His point at the time was that a user who only has say a Kindle and a small collection of books is *not* even a target user for calibre. That if they really want to get PC software involved that they will just use the Amazon Kindle software (and similarly for Sony users with whatever their software equivalent is). And that calibre is really targeted at either people who want to shift formats, and/or who have very large collections of ebooks (the latter being a minority though over time that is obviously going to change).
I sympathise with both sides of the argument. I put calibre on my parents PC, but they use only 1% of the functionality. I source all the books for them, take care of all the metadata gathering and format shifting etc, and they just use calibre to load books onto their Kindles and keep track of what they have read, plus browse through the collection sometimes. And yes the UI has loads of stuff they have not a clue about, but I've stripped stuff out where I can and given them a basic set of instructions to keep them going. Would they be better off with a UI that supported only that use case? Of course. But (a) it needs to exist, and (b) it would be something I have to support for them on top of my own calibre usage. Meaning if it is a completely different program I have to find a way to export/import between the two for instance.
With that said, as soon as you need just one more feature like converting book formats, you have a game changer. The level of technical knowledge involved is beyond what most of the public out there are prepared to learn or care about. I would suggest they don't want to know about an azw3 versus a mobi versus an epub, let alone all the minutiae involved with conversion parameters. You can try to wrap it up in a really dumbed down UI, but users like my Mum would still never "get it", and the slightly more technically inclined will be frustrated by not knowing what it is *actually* doing, or that their books don't look right because they have no control over the output.
I don't know what the "perfect" answer is, neither over the years on these sort of threads has anyone else come up with an actual practical suggestion. Perhaps there isn't one, and it is just the nature of the beast. So arguably the correct approach has been to just let calibre continue on as is and stay focused on providing the most functionally awesome application out there for those users who are slightly technically inclined or at least willing to roll their sleeves up to learn. There will always be people out there whose interests in life include reading but do not include having to learn about electronic book formats and all the crap associated with that. At this point unless they have a friend/relative willing to do stuff for them, calibre just isn't the right program for them, and maybe it shouldn't try to be?
As for being baffled by the plugin system - please read the Introduction to plugins
sticky thread in the plugins forum, and feel free to feedback anything at all you are still confused about. I am more than happy to try to clarify the documentation if you can help describe what are the pieces that are missing for you. From a donation perspective I would obviously love it if far more users had the knowledge of and confidence around using plugins
. I know in my own usage and from the hundreds of comments people have made on the plugin threads that if you find the ones that scratch your particular itch they become an indispensable part of using calibre.