Not always. M:TG has always been sold as a collectible card game, and many of its early cards are extremely valuable.

Aren't the ones that are valuable mostly misprints and low volume variants?

Not necessarily variants or misprints, but many old powerful cards are extremely expensive. By this point the volume is much lower just due to time, but many cards from the first ~4 sets are worth hundreds to hundreds of thousands of dollars depending on the card and condition.

No, but they are from the first couple sets when production runs were smaller. WotC has made a promise to the community that they will never reprint (tournament legal versions of) some of those early cards which helps keeps them rare and expensive.

You wouldn't really want those cards reprinted anyways. They're very overpowered and seem like amateur design if you look at them through a lens of the rest of MTG design history.

You may be thinking of the different border on cards from the alpha and beta sets as variants. But that's the way every card was printed back then.

M:TG wasn't immune to the collectibles glut in the 90s. The Fallen Empires set, which came out in 1994, was so overproduced that you can still get factory sealed booster packs for the same price as current expansions.

In fairness, only Hymn to Tourach was really any good long term from Fallen Empires.

Limited editions of video games seem to do decent. Many runs sell out and then buying them on amazon costs 2 to 3x the price of the limited edition originally. It is extremely rare for such an item to go much above that these days, compared to some games from the past where a new copy is 10x the price or more, but it is still enough to count as collectible.

But is some limited edition swag gonna be worth 20x in a few decades? I think not.

You are confusing terms. "Collectible" doesn't imply that something will gain or hold value.