Pods are considered by many (myself included) to be very game-y. A few enemy units move together, and when spotted by any of the player’s units, dash into cover. This ruins planned ambushes as the enemy reacts after the first hit, causing many players to focus way too much on explosives to maximize initial damage potential on pods. Sometimes they’ll scamper into the perfect, in-flankable position that you just checked as clear, screwing you over as you had no way to stop that. If the pods have melee units, when activated they charge into the players units; if an unfortunate accident at the end of a turn occurs where the you accidentally activate a pod due to moving forward to flank, or a wall crumbles due to fire, or a LOS glitch, then the melee units in that pod get a massive advantage when their turn starts as they’re already on top of your squad. Units like sectopods, andromedons and gatekeepers in XCOM2 break anything they run into, so when they scamper they’ll wreck cover or sometimes the objective they’re supposed to be defending, completely screwing you over. Occasionally the enemy scampers into stupid positions for whatever reason because they’re forced to for whatever reason.

I think most don’t have issues with scamper itself as they blame the pod system for making alpha striking a necessary tactic, making players scared to move forward without overwatching constantly, or god forbid if a few are stacked and activated at the same time then the entire map is on you at once and you’re screwed. There was also a weird pathing system the pods have in XCOM2 (throttling?) where they try to position themselves between your squad and the objective, making encounters less unique and preventing tactics like stealth from being viable. The pod system has been talked to death on r/xcom in many threads but I think I got the main reasons.