I quit like 2 or 3 years ago? I remember playing this game during a time when reddit was sucking Vespa off for everything, and quit around the time they've been turning on them (rightfully so.)

This game at the time had an issue where upgrades kept getting power crept by new systems, which increased the amount of time to max out characters significantly if you're F2P, but not if you pay. That's their way of getting your money when you can just use free currency to purchase a unit instead of rolling the gacha.

The amount of resources you need to max out a unit even then was absurd and it would take months to do. I was at the point where I finally had a full team and was content, and then several new time gated upgrades got added and I got fed up. Literally a job of a game, and the gameplay itself isn't even that good. People who pay are strictly better than you and there's nothing you can really do about it.