you can get most of the battery cell upgrades by opening chests from exploring (and where the chests are becomes obvious if you collected a few old maps) and following the main story. The problem is exploring the depths isn’t all that fun. I never even used duping to get battery in my original game- by the time I explored the depths fully I was maxed out.
its not insane unless you’re doing completionist stuff, you can easily cap a few sets of armor for key purposes just with chest loot and some monster mashing. I created a second game on another user account after my first game (with duped gems, etc) and its not really grindy until you try to max out like a third set of armor.
My highest play time game is probably minecraft, and my recent go-to is slay the spire.
Sequels are seen as safer profits (there is an existing market) so they get more investment and more investment tends to make better games.
This doesn’t mean its what people want, it just means that name recognition means its cheaper to market a hit game with previous versions acting as a marketing boost. Its a feedback loop.