>none of them seemed to face any issues with being made in Unity.
I'm sure they did. But I wager there is no such thing as "smooth development". Every engine has its quirks, every team has its odd dynamics and clashes.
engines are there to make development smoother, not smooth.
>it's bound to have a bunch of shovelware made on it with how many resources there are for learning it (and Unity being free), but it's popular for a reason.
To be fair, that one is more on Unity. You had to pay to remove the splashscreen, so that meant low effort titles would have "MADE WITH UNITY" front and center, where higher budget titles could remove the logo. It was great for awareness, but it completely reversed the perception of the engine quality as a result.
(disclaimer: I used to work at unity)