There are too many きかん and they are pronounced in the same way (pitch) so the accent mark does not help.
(Even when the words are pronounced with different pitch, they can be different in region - what can we do with that?
Like 橋 hashi/bridge and 箸 hashi/chopsticks. In Kanto area people say it hashi (LH*) and hashi (HL*) but in Kansai they do not use the same pitch.) (*H means high and L means low here.)
器官、期間、機関、既刊、基幹、帰還、気管、奇観、旗艦、季刊、貴官、貴簡、亀鑑、帰館、帰艦...
Same goes with せいじょう:
正常、政情、清浄、性情、性状、星状、聖上、星城、成城、製畳...
From the context I can narrow them down a little:
機関 or 気管, or less likely but 期間 is also possible.
Most likely 正常 but 清浄 and 星状 are also possible in a very special situation.
It's ridiculous if you believe writing it in kana like その キカン は せいじょう に うごいている. or その きかん は セイジョウ に うごいている. make the meaning of words clear. It does not make much difference from そのきかんはせいじょうにうごいている。 The only thing I can think of is that people who are not familiar with the language can recognise each word (where it starts and where it ends) in the sentence because of the spacing, but again, it does not help you to understand the meaning of the words at all.
When everything is written in kana, you have to think more than twice to understand what is written, and spacing and accent mark do not really help. When written with kanji, it is very easy to grasp what's written just at a glance.
Why do we need to change the language into something more inconvenient and difficult?
東京電力福島第1原子力発電所から高濃度の放射性物質を含む汚染水が漏れている問題で、政府は3日、約470億円の国費を投じ政府主導で解決する方針を固めた。国の全額負担で原子炉建屋への地下水の流入を遮断する凍土壁を設置するほか、汚染水を浄化する装置も増設する。東京電力主体の従来の対策よりも前倒しで事態を解決できるようにする。
福島原発、汚染水対策に470億円 政府が基本方針 :日本経済新聞
This is from an article released this morning (Nikkei.com).
Even without reading the whole text, it is easy for me to see that it is about About Nuclear plant in Fukushima, radioactive materials, goveernment is taking care of it, blocking the underground water with a kind of wall made of frozen soil, etd. "at a glance", because kanji is ideogram. I say "at a glance" and it is not a joke or exaggeration for native (and maybe fluent) speakers. Of course, to understand it fully and correctly, I need to read the whole sentence.
Another advantage of using kanji is that if you know the kanji, it is easy to guess the meaning of the words even when the words are rarely used or something completely new to you.
The word 凍土壁 is completely new, but because it is written in kanji, I can guess that it is a kind of wall (壁), made of soil (土) that is frozen (凍). Some explanation is given in the article (凍土壁は建屋のまわりの土を冷却剤の循環により凍らせて地下水の浸透を防ぐ設備) but before reading that part, I can understand what it is talking about and what the government is planning to do.
If the article is written in kana without kanji, I'll be clueless, because the sound とうどへき does not make any sense.
In a nutshell, kanji is an essential part of Japanese language, and without using kanji, our daily life will be extremely difficult.