I feel like the format has changed a lot with new printings and restrictions, but I think it is not necessarily bottlenecking in a critical mass as much as it is turning directions like a winding road.
Back in its heyday, it was gushatog, oath, and trinishops with an occassional fish deck (literally blue fish). That was 2002ish. Then planeswalkers came out and that card type got pushed to the limits with narset, oko, karn (consider that the OG "this is too busted" PW, Jace TMS, is now virtually unplayable!) But now we're seeing a new direction to the game - creature's matter/self mill. With Thassa and Jace o' mysteries and underworld breach to go along with arcanist, delve spells, etc., milling yourself has become a win condition.
Cards like DRS started the creature push, but now vengevine, hollow one, stonecoil, collector ouphe, and others have made the game slow down from the "chain my gushes" days of magic and made the attack phase as relevant as it was in old school times.
The only storm cards we really got any time recently was PO, and since then ouphe, karn, narset and such have just punished the "draw deck/drop jewelry" strategies. The game looks fundamentally different, but not in that there's only 1 viable deck from saturation. As a guy who always hated the shops/blue-draw/bazaar triangle of the vintage format, I'm very happy that we've finally broken that trifecta. Those are still powerful axis cards, but decks not even running or needing those engines are doing great things. BUG is a deck, oko oath is a deck, thassa+consult is a deck, hollow vine is a deck, fastbond is a deck, and to a lesser extent fringe decks (like my own welder deck) have become playable and respectable in the meta - hell, even freaking NINJAS...I repeat, NINJAS, have the ability to win. And of course dredge, PO/storm, shops, and xerox are still decks. That's more diversity in viable strategies than I've ever seen in vintage, honestly. Any of those decks can play well and win, whereas before only the three axis REALLY could win and fringe decks had barely a puncher's chance. I think Vintage is as good as ever, if not better.
Put it this way - I ONLY played vintage from 1994-2008 and then modern came out. Vintage got stale to me and Modern became my go to format. But in the past year or so, Vintage is now my fave format again. That says a lot about the meta to me.