As Replicant said, the additional costs associated with DLC and other post-launch content are purely optional. Online subscriptions are optional as well. You do not need Xbox Live Gold or PS+ to play single-player games.
Also, what would you prefer: New games costing $80 new, with any add-on content being free, or games remaining $60 with the option of buying DLC/expansions/MTX?
The declining price of software combined with the rising cost of game development (which is not offset by market growth) meant something had to give at some point. While I don't defend the increasingly aggressive and often predatory ways many publishers monetize their games post-launch, I do completely understand why these businesses might seek to monetize their games at all.
Are we really though? We have countless massive wide-open game worlds with 60 hours worth of gameplay. Fighting games still have rosters as large as the historical norm (and back in the 90s, when you had a roster expansion, it meant an entire new full-price re-release of the game, as we saw with Street Fighter 2 and Mortal Kombat 3). Platformers still exist and are similar to or larger in scale than ones from several generations ago. Back in the 16-bit era, most games aside from JRPGs could be beaten in a single afternoon. If someone wanted to charge $80-100 for a 2-3 hour-long 16-bit platformer or action title today, they'd get laughed out of the room, yet that's what we paid for back in the early 90s. Today's gamers frequently don't factor in intangibles like replay value, and instead go by the length of a single playthrough (for single-player games, at least), and games last an order of magnitude longer on average now than they did 25-30 years ago when the cost of a new game was at its peak.
Sure, there's probably a few notable examples you can point to where a game has less content on-disc than a game in the same series did in the past, but in general video games are one of the best value propositions right now in terms of what you get for your money.
Microtransactions are NEVER optional. Games are being made deliberately worse to entice people to buy them to increase the fun of the game to a level it's supposed to be at. That isn't optional, no matter if you buy them or not. Having less fun games is an underappreciated cost.
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