I disagree. Some games absolutely improve as you progress. It's also not a "defense" of a game. Like movies, books, and even television, some entertainment experiences take their time to set up characters, the world, the plot, but since games are interactive, there are times when setting up gameplay mechanics are necessary. I've definitely played my fair share of games in the past that overwhelm the player with mechanics right out of the gate, and I personally feel like those games burn out fast because they blow their proverbial load so quickly, or the systems are so complex so soon, that it's easy to forget x mechanic or y mechanic. Sometimes it's smart to ease a player into the mechanics, as well as a way to keep gameplay engaging with a "carrot on the stick" style approach. It really depends on the game and what it's trying to convey.
The inFAMOUS series did a really good job of meting out mechanics, letting the player have fun with the new powers, then dangling a new power/upgrade in front of them that fostered a "just another 30 minutes, then i'll stop playing" type of result.
While I can appreciate a God of War-esque epic start to a game, I'm also not against a slow burn. Sometimes, a game just doesn't click with a player until later on. One approach isn't better or worse than the other, and some games work well with either approach.
Day's Gone is a recent example of a game that I feel most definitely gets better as it progresses. Not just the narrative, but the gameplay progression as well. The first two or so hours are purposefully limited in what the player can do, and then it opens up shortly after, and they did a good job of tying weapons/abilities/locations into the narrative, so it made sense why your character isn't a walking arsenal at the start of the game.
Pacing is also something to consider when introducing new mechanics to the player. Sure, you can drop in all of the mechanics at once, but like I mentioned before, it can overwhelm the player to the point where they aren't even experiencing a fraction of the content you've produced, because they just stick to the mechanics that help them get from A to B, or give up in frustration when they encounter a scenario later on in the game that requires you to have had knowledge of y mechanic, that you totally told them about at the start of the game.
Being able to pace out progression/mechanics, is a solid way to ensure that the player is experiencing multiple things: 1) A smoother escalation of mechanics, especially if your game has a lot of complex systems. Giving them time to absorb and "master" one mechanic before being introduced to another.
2) The player is less inclined to burn out on your game and feel like it's "getting repetitive" because you're introducing newer mechanics/challenges/mission/level design to them at carefully considered intervals.
Number 2 is a lot harder to balance, because the threshold for player "boredom/interest" varies from person to person, so you work really hard to strike an acceptable balance. Same games do this well, some games don't.
Anyway, the tldr point is that the "it gets better at point 'x'" is totally a valid opinion to express. No different than when talking about a tv show that maybe starts off wonky for the first two or three episodes, but then gets its hooks in you at episode four and beyond.
