English grew out of an older "synthetic" group of languages, but in modern times it's become much more like Chinese and Chinese-like languages.
Now, regarding "spelling", if a single spelling can handle the requirements for guiding the pronunciation of several words, that single spelling can easily be handled in English. Word order will tell the listener or reader what part of speech controls its meaning.
"Their" and "They're" are, in fact,both personal pronouns, and irrespective of their different meanings, there's really no purpose served in reserving two different spellings for them.
Now, how many conjugations and declensions in Latvian have you memorized this year ~ 20 perhaps, or maybe 35 ~ or more! Now those people need to use sentence diagraming just to figure out what they said.
And the Poles could use some vowels.
WTF? Over.
Desist immediately or I shall have you thrashed about the legs with a bamboo cane. Return to your day job of translating Latvian folksongs into medieval Lithuanian.
"Their" is an adjective of possession. "They're," is a contractive verb form, IOW, short for "They are."
Capeesh?