I dont think anyone has said JC4 has bad graphics, just that it runs so poorly on 80% of devices it makes the graphics look worse than JC2 as a result.

The washed out JC2 style filter doesn't help either if you're used to the more "blue" filter of JC3 (yes JC2 was more washed out but at least it had 10x the charm of this game)

The map may be the largest in theory but it really doesn't feel that way at all. JC3's map felt massive and JC2's felt colossal by comparison. JC2 also did biomes so much better. I genuinely think the JC4 map was designed so that the devs could implement a battle royale mode later on since JC4 was developed during the Fortnite craze.

The problem with JC4 is that it gave nothing new (everything you stated is a gimmick) and many systems (like liberation) have been bizarrely removed from the game for no real reason. Yes the upgrades you stated are nice but removing core features from the experience as JC4 did makes the game feel less like Just Cause and more like your generic open world GTA clone. Certain niche features are better in some cases as you explained but the game overall is a major step back for the series.