Even if that's true (and I share the sibling's skepticism), vendor A's incompetence and poor product quality is not meaningfully described as "lock-in" to vendor B - especially so when there's a readily available vendor C (Firefox) that doesn't share these ills.

I've gotta raise an eyebrow on that one. If it's a major rewrite to support a new plugin authoring language, your plugin architecture was a terrible mess to begin with.

Given that we're supposed to believe that New Internet Explorer was pretty much a from-the-ground-up rewrite, I can't imagine that their plugin architecture is a terrible mess.