Mozilla hasn't been ported to the Amiga specifically because the hardware is to old to support new software (duh!) - until the AmigaOne.
Also, your claim that Mozilla runs slowly on new PCs is nonsense. Even on my Celeron 800, which is pretty slow by today's PC standards, the browser starts instantly.
As for your "spaghetti code" stuff, note that this product is not even 1.0 yet. Also note that there is a much smaller "embedded" version of Mozilla that could pretty easily be ported to PPC hardware. Finally, note that there are rumblings in the Mozilla community already about ripping Mozilla into separate apps for 2.0.
Anyhow, with any luck Mozilla will be ported to Amiga OS 4.0 sometime soon and put those ridiculously priced, underperforming ($50!) Amiga browsers out to pasture once and for all.