Yes it is and you need to get ON the high horse. Apathy, ignorance, and sloth are unacceptable. Disengagement is resignation.
If voting was the be-all-and-end-all of civic engagement like you say, then people incapable of voting like minors, felons, people who lack access to voting facilities, and undocumented immigrants wouldn't impact society in the massive way they do since apparently voting eclipses all that. And yes, I know that don't vote =/= can't vote, but the outcome either way is the same since these people aren't participating in elections. And what of people who
just vote, and don't participate in meaningful civic engagement any more than that? You'd be hard-pressed to convince me that those people aren't "disengaged" from societal progress, and by your definition, resigned.
Yes, voting is important, but it's silly to say that it's the absolute summit of public participation. To say as such implies things such as parties like the Greens and Libs are pointless. After all, they never win elections, so their civic impact is miniscule,
right? Additionally, with regard to vote-shaming (which, anecdotally, I frequently see correlated with "Just Vote." type people), like literally what is the plan with that. Even if you get the vote, you didn't expand the base, and you didn't persuade someone to your ideals. You essentially bullied someone into doing what you want, and they will not fight for it anywhere else down the line. And again, if voting was truly the be-all-and-end-all, it would
only matter that you got the vote.
We live in a society that just doesn't reflect voting as being a panacea of social stagnation. All my points aside, the complicated, interconnected nature of people in general means that no single method will spur people to civic action. Voting has to coexist with, and not overshadow, things like organization, volunteer work, fundraising, protest, even purposeful abstention from elections in order to remain meaningful.
And as a side note, I'm deeply skeptical of any argument like "here are some reasonable motives why someone may abstain from voting" "nah".