No. "IF CAPABLE" refers to the ability of the communication suite in your aircraft to comply with the directive to monitor guard, not your willingness to comply. It's not a suggestion, it's an FAA directive.

It doesn't say you have to remain on guard to your own peril. If you need to communicate with other sources using VHF 2, then you do so. Then return to guard.

CBreezy hit it. We are required to maintain a continuous link with dispatch via ACARS or other less capable means for the very scenario you brought up. It's their job AND the crew's to maintain awareness of changing wx conditions at destinations and alternates, making changes as necessary.

Gaining SA on deteriorating weather via happenstance by overhearing information on AIRINC that happens to affect you isn't my idea of a plan. Dispatch should be doing their job but as you said, it's wise to cover one's own ass. Any competent crew should be seeking that information anyway as a matter of normal procedure, not because they get lucky on VHF 2. ACARS, ATIS, AIRINC, FSS, SATPHONE..... whatever it takes to get the information one needs to make the best decision and complete the flight safely.

If that means leaving guard to accomplish it, then so be it. Just return when you're finished. I could even agree with the decision to choose AIRINC over guard during rapidly changing wx conditions for a portion of the flight - just not as a matter of course for every flight. I doubt that's necessary with most aircraft these days equipped with ACARS. You do not have the option to disregard procedural directives and continuously monitor something else, when your aircraft comm systems allow compliance, just because you might hear something useful on another freq.

Here's a litmus test for you: Next time you get an FAA line check, would you be willing to inform the check airman of your radio plan and then use it for the whole flight? (and spare me the story about how you didn't monitor guard on your last checkride - not everyone is going to catch every error.)