I mean, think of it this way: it comes down to how often you come across words in any language including English (even in ENG: you may forget how to spell words correctly if you don’t use or encounter them often), kind of the same logic with Kanji: a Japanese person doesn’t know all Kanji in the same way English speakers doesn’t know every single word that exists in ENG.
There are over 5000 Kanji but only about half of that is used in Japanese or closer to 2136 while the remainder consist of ones only present within technical jargon (medicine, science, politics, etc.). or certain Kanji only has limited uses in some words (but mostly written in kana). That is also accounting for grammar being “straight forward” more than English or Euro languages.
The “real” hard part is numerous readings (depending whether it’s paired with kana or another kanji, reflected from kunyomi & onyomi plus nanori when applied in people’s names). What I hate about most online translators is that it often gets lost in translation (like words used in the wrong context but on their own it’s correct, however not right for the situation or topic at hand).
The lack of phonetic information is a challenge. If you see an unfamiliar English word, you can guess the pronunciation, and usually be pretty close (sometimes you’ll get a phoneme wrong or stress the wrong syllable, but listeners will be able to infer what you meant). With kanji, as well as not knowing what it means, you have no information of how it’s pronounced. It is theoretically possible for kanji to exist which not only lack meaning but also have no pronunciation, and indeed, there are about a dozen meaningless, soundless “ghost kanji”that ended up in Unicode due to bureaucratic errors at the Japanese standards agency.
You can do this to an extent with kanji, as well, it’s just something that really only gets easier the more you study Japanese, though. When you start getting more proficient, you can usually have a pretty good shot at guessing the pronunciation and something of the meaning in context, but the difficulty is certainly really front-loaded.
Of course, then you have some kanji that just have 100 different readings and you just have to go memorize those, so there’s certainly room for improvement.
For contrast, in Finnish, you’ll know exactly how a word is pronounced if you know how it’s written. English has exceptionally nonsensical pronounciation.
You could have done that in English at one point, but then we changed all the vowels and added in a ton of words from a different language type.
I had a friend give me kanji learning cards and she had to write the pronunciation of each word for me. It had me stumped that similar kanji had no phonetic relationship.
I can sometimes read a kana word in under 30 seconds. I’m that bad. At least the symbols that look similar often sound similar too.
Depends on what you mean by “similar”. If you’re looking for the right thing, there are often a lot of phonetic hints in kanji.
For example, 矢 and 夫 sound completely different, totally unrelated. These are pretty basic kanji though; I think it’s analogous to how O and Q are totally different, or i and j.
If there’s more complex similarities though, then yeah there can be an implied phonetic relationship. Look at: 同胴洞銅恫桐粡. These can all be pronounced the same: どう (dou). Though, many of them have kunyomi readings that are totally unrelated.
An impossible joke in kanji: