I disagree. I think the only RE game where the story was 'cartoonish' was RE4 and maybe CVX. But recently the science behind the series hasn't gotten any more ridiculous than the earlier ones; they still use viruses and have actually explained more of the details about how people transform. The risk of infection is still present but has other methods than just the usual physical contact (Ex: fog or injection) neither of which are too unbelievable.
If you dislike the way the games have progressed mechanically, that's understandable, but IMO, RE's one of the few series that hasn't done too much damage to itself plot wise. The settings have changed but I thought that was to be expected since Raccoon city was destroyed and so was Umbrella eventually.
However, this isn't detrimental to the story at all. They always painted a bigger picture behind Umbrella's power and influence (both 2 and 3 did this) and 6 was the one to expose who the real culprits were while 5 tied up the loose ends with Wesker. Now it just depends on it's delivery from this point on for whether or not it's all effective.
