1) resources you can buy with real money;
2) massively increased rewards due to active gameplay;
3) daily gambling rewards;
4) reset-based system when you're grinding to reach some some level, only for everything to be reset for some incremental reward.
Worst offenders I tried are NGU idle (overwhelmingly positive steam rating), Trimps, the perfect tower, which aren't actually idle, but rather incremental.
A good rule of thumb is - if having a bot for a game would put you in a massive advantage then it's not an idle game, but rather an incremental game - a genre that is designed to be played for 'idle' amounts of time (forever basically) but actively, so will likely feature as many dark patterns as possible to keep you glued (and paying).
On the other hand, here's a game like Melvor idle - true idle in spirit with little differentiation between online and offline, no resets, no gambling, yet still with plenty of depth around optimization. Relaxing, yet engaging.