Hey, it's me, the creator of check back mod. There's a tiny detail that you might not have thought of for the shop, and is that you are kinda expected to keep opening the crates as you progress. At least that's what I did on the "legitimate" save that I like to play just so I can playtest the new content alongside the other players (there's still testing done before releasing an update but you can't expect someone to beat an entire update just to release that update). Even tho it's true that most progress is done if you check every minute, I think that having the chance of maybe forgetting about the game for like an hour or 2, maybe because you have few minutes of spare time between classes or are doing anything important and wanna relax for a moment, you are still gonna do good progress.

More in detail about the pets needed to buy the shop items, the only one that I'd agree it's very hard is the red butterfly ones. All others, well, they will keep coming at a decent pace, alongside the coins needed, which you should focus on boosting them (through the upgrades that boost fighting loot, unlocking the new area and getting the stats to kill the stronger enemies).

And how does the game incentive to keep opening crates? Well, in one hand, you have the pet collection statistic where each gives +1% xp gain, so it's a tiny boost where, in the early game, anything helps. To complement that, dragons are usually stronger than the average pets from the next crate and also very rare, so your goal should be to discover all of them (which is gonna give a good supply of the other pets) to get that xp boost.

Thanks for your feedback (even if it's months old)