Most AAA base games cost ~60 dollars for the base game and the DLCs add on top of that.

I'm not gonna be mad about the price, a game is cheap in terms of hours entertained compared to a good movie which costs about 10 dollars for about 2 hours of entertainment.

The issue is not the price. The DLCs is also not inherently bad, like you said. For instance, Borderlands 2 is known for having an excellent base game and an exceptional bunch of DLCs, one which became so loved and popular that it became its own spin off game (Tiny Tina's Wonderlands).

The issue is that companies use DLCs as an excuse to charge money for small amounts of content. They make smaller games, still charge full price, then make DLCs that are relatively small and charge a lot for them.

Using the above example, Tiny Tina's Wonderlands have DLCs that cost 10 dollars and feature a single dungeon (that takes ~20 minutes to complete) with a boss that was an enemy in the base game which got enlarged slightly and given more damage and HP. The community understandably was pissed - but they kept buying every single DLC they pumped out, which reinforced the behavior.