U dont think tht some ppl hav made radicl changes 2 englsh spelling?
In the long run, no they haven't. Despite a mountain of alarmist claims, there's no evidence that l33t and other online orthography games have had any lasting impact on the offline spelling of younger speakers (just as most teen slang is ephemeral and never gains any footing in the language).
And it's bad analogy for the simple reason that the online environment has made it easier
to use kanji, not harder. Before it took a great deal of rote memorisation to keep in mind how to write anything but the most common characters. But nowadays most input methods give you dropdown lists of alternatives based on phonetic spellings. As a result, there's been an upsurge in complicated, obscure characters that were on their way out before.
I really don't know about Japanese but you couldn't make a phonetic (or different in general) English spelling system without reunifying the many dialects of English first.
This would be less of a barrier for Japanese since it's not a plurilocal language and the normative pronunciation standard is more securely entrenched.