In general, when dealing with an introvert, social power dynamics are not generally a key issue. When someone with social anxiety, social power dynamics matter a great deal - and the exact flavor of dynamic that can be a trigger varies from person to person.
Enabling shy or introverted players in a social game setting is just perpetuating their suffering and doing no one any favors. Not them, nor anyone else at the table.
Unless someone has autism or aspbergers or severe, clinical social anxiety (I know several who check those boxes), then if they play D&D they should speak up from time to time, is all my point is. If they barely even try, that's either lazy, or staying in your comfort zone. If you're not trying to expand your comfort zone towards being more at ease during human social interaction with close friends, then what's the point, right?
It's not like players need to give a rousing speech in full character voice if they don't want to.
The % of air time that each player takes at the table, shouldn't be so lopsided that one or two players steal all the daylight. But if the other players don't even try to make a peep, how can those players who do love the limelight even consider their feelings? This is an inherent problem to any round table. And in any other setting, if you have a seat at the table, it's because your opinion and your contribution should be considered, and it's up to the moderator (the DM) to make sure that everyone's voice is heard. And if you have no business being at a meeting because either you don't want to contribute, or aren't interested or motivated enough to even bother trying, then it's perhaps time to consider ceding your seat to someone who does.
This topic intersects with playstyle and DMing style greatly. The proportion of each session devoted to combat matters here. If you play, 33% of each pillar, combat, social, exploration, and contribute 0 to social, you're missing out on 1/3rd of what the game can offer. But if your game is 50% combat, and you have 6 players instead of 4, then players sharing their combat time with more players are losing 50% of their turns, and spending that much time each session twiddling their thumbs, waiting. That is a detriment to their enjoyment. Nobody likes waiting for others' turn to end.
More turns, more waiting. That's tolerable or even exciting when other players are doing interesting or exciting things on their turn. But just phoning it in, and never opening their mouth and shouting even "For Greyhawk!" once in a while, gets pretty dull after several years of that. Silent players impact every pillar of the game, not just social interaction specifically.
If you contribute 0% towards social interaction, and have no interest in increasing that to 5-10% even, then it's definitely time to play a CRPG or MMO instead, in my opinion. Just keeping a seat warm and rolling a d20 every ten minutes does not a valuable player make.
I have tried that, and found, as I was quoted in the OP of this thread, that trying to game with people you don't know can be eye-opening. You can, and probably will, find people that you barely know that you enjoy gaming more with, than the same old same old comfy shoes that maybe have a few holes in them and should probably be replaced for a fresh pair. This isn't just D&D related even. Meeting new people is great, and gaming with them can be great. Sometimes you outgrow old friends and need to make new ones, and D&D is great for that too, even in your 30s. Some of my oldest friends have turned out in the end to be some of the people I least enjoy gaming with, and some newer players I have way more fun with. It's definitely good to get out of your comfort zone once in a while and mix it up, there are billions of people on planet earth and plenty of interesting and exciting interactions and experiences to be had through gaming.
All I'm saying is, don't miss out on those experiences by staying married to gamers or tables that aren't doing it for you. And for D&D, silent players just don't do anything for me. And I know I'm not alone, because others have brought that up several times, both in this forum and in person to me. Silent players are a thing in D&D, and to me, a type of problem player.