Back in the day, you could try out new things and play 10-20 turn games where both sides had winning chances. The odds that your opponent had anything approaching an optimal meta was zero.
Now, especially online (Arena), you’re just going to get curb stomped if you aren’t playing one of the few optimal metas. And since the games hinge upon either side getting an unstoppable engine going by turn 3 or 4, if you get a drought or flood (or mulligan), you’re basically completely dead in the water. Same for your opponent.
The net result is that it feels like something like only 15%–25% of games are actually competitive, because either you or your opponent gets fucked by too many, too few, or wrong color land draws, or for whatever reason you don’t draw the cards you need within the first few turns.
A game where 80% of matchups are effectively no contest is not fun.