Most hanzi in Mandarin are partly phonetic. See https://en.wikipedia.org/wiki/Chinese_characters#Phono-seman.... It's generally not based on radical, but on the so called phonetic component. See say 元, 远, 园, 院.

As the comment you're replying says, it's not meaningful (at least from the perspective of language learning). For example, the characters you give are still pronounced differently; yuan2, yuan3, yuan2, yuan4.

That's why I said it's partly phonetic. From the perspective of language learning I think it's extremely helpful to be able to intuit from the phonetic component that they will sound similar. I would also say that the tonal pronunciation differences are not that significant as the main distinguisher in Mandarin is the usage of compound words (2+ hanzi). Consider the fact that in China there are very few people who speak in the "proper" correct CCTV way. Most people will have large tonal variations from dialect etc. Compound words are the key to intelligibility.

On the topic of tones, I'd like to clarify something. It's true that few speak in the CCTV way, but to each Mandarin tone there are several realizations (perhaps altered by context) that people recognize as belonging to the same tone. That is, there are in Mandarin (and in any modern Chinese language), tonemes.

Note that when we survey the multiple dialects in China, we see that they more or less preserve the Middle Chinese 4 tones, even though the tones' realizations have evolved so greatly such that the Middle Chinese tones' actual realizations are but unreconstructible.