If it came to be that it was easy to take infinite turns on turn 1 or 2...like Vault key x100 consistently, then yes, it would be healthy for the format to make a fundamental change like that. I'd also have to think the community would embrace it, or else you are just playing a game where every deck is a mirror match and all end on turn 1 or 2 to whomever assembles the combo first.
Do we think the format is anywhere near this critera with companions? Format diversity has ceriantly been challenged before and at any given time there really are not that many viable archeypes outside the pillars.
First, the pillars themselves barely hold now. They used to be workshops, ritual, mana drain. Now they are more like Bazaar, Workshop, FoW. And we have cavern of souls which is becoming almost a 4th pillar, and oath of druids which is a long-standing format staple. That MWS/Ritual/Drain pillar model is already obsolete. Mana drain is almost never played anymore, and ritual only appears in a deck or two, and rarely often.
Also, I wasn't saying companions are like 100x vault key. I was saying, in your example of if Time Walk was a problem and easily recastable to that level of consistency (like if the card had retrace and always started in your hand), then, yes, WotC would likely prefer making rules to nerf one card as opposed to letting the entire game fall to pieces and devolve into all Time Walk.dec mirror matches.
There's a point to where holding on to the "purity" of the game actually reduces the playability of the game. This happens in all games where factors change. In a game like chess, where the rules have been static since the beginning and no new pieces were introduced since, there's no need for change. In magic, with an ever-growing card pool, changes to the rules are inevitable. It's more like football, where television became a factor and players went from 30-year-old 195lb cigar-smoking bruisers to 260 lb physical freaks that can run a 40 in 4.3 seconds. The rules HAD to change.
Yes, fans hate some of the rule changes...but they still watch, and football has overtaken baseball as the American pasttime now. Similarly, players had an outcry over the rules changes to damage stacking and mulligans, but overall, the rules were good and allowed for different cards to exist. How broken would ballista be (in formats that care about ballista) if you could stack damage? How many times did people gripe about losing games strictly due to mana screw? London mulligan has fixed that tremendously. There's the side-effect of adding consistency to bazaar decks, but honestly, the reason those decks are so good have less to do with London mull and more to do with them getting Hollow One recently and 8 devastating pitch spells in Modern Horizons.
There will always be purists who want the game to be static, but they are the minority. MOST people that like new cards and new mechanics coming into the format realize rule changes will be necessary on occasion. The wishes got erratad, the "exile zone" became a new thing, emblems/PWs, damage stacking, mulligans. Hell, even deck size was once 40 cards! Rule changes are a necessary part of the game. The only ones who rail against any changes in the rules are those who want to freeze it in time. If that's the case, play OS. Or, stop printing new cards with new mechanics and any interactions with old cards. Those are your only two options.