The frustrating element of these rooms comes from how you get them. The only way to change what rooms you have is to use the Change command, which swaps out every room that is not locked for a completely random new one. There is no way to control what properties or formation the new room will possess. This means that if the player wants a room suitable for a melee unit, they need to continuously swap out rooms until one appears that has plenty of front-row spaces and has an effect that is half-way decent for a melee team. It can take dozens of Changes to finally get what you want.
This kind of mechanic is not that uncommon in videogames, and RPGs in particular. For example, it happens quite a bit in Persona 3 when fusing Personas. While you always get the same Persona whenever you fuse two old Personas, the spells and powers that the new Persona inherits from the old ones is randomly determined. So whenever my brother fuses Personas, he always has to continuously cancel fusions and try again until the resulting Persona has the right moves that he wanted it to inherit. I have seen him cancel fusions thirty or forty times in a row until the Persona finally got the right moves. The same kind of thing can happen in older RPGs that emulated some kind of dice-rolling mechanic for coming up with stats.
These kinds of mechanics are just annoying and frustrating. The randomness of these outcomes forces players to constantly try them over and over until they get what they want. It can also force players to be frustrated when they pass up an option, hoping to get a better result, only to regret it later since that option was the best outcome they came across. I know that has happened to me. Since these kind of situations rarely spell out what all of the possible outcomes are, it can be difficult to judge whether an individual outcome is good or not.
If I was a designer for Soul Nomad, I would have argued against swapping out rooms randomly. Instead, I would have elaborated more on the "home" system of the game, where a character can purchase certain rooms. I would have allowed the player to buy rooms for every unit (not just one unit), and have expanded it to include the ability to unlock or purchase new formations. This means that the players would have a greater flexibility in designing the units they want. Intentionally limiting this flexibility with random elements doesn't really improve the experience on the player. This change would eliminate the possibility of "bad vibes" hanging out in a new rooms, but that feature doesn't really do much in Soul Nomad anyways.