huh..! this is a tricky one... i have a really hard time boiling down any game to "conventional", since usually even very by-the-book games have at least one cool thing going on. this is couple with the fact that i rarely play AAA games, which are more likely to be conventional...
the two that come to mind most recently are Touhou: Lost Branch of Legend, and The Witcher 3. even then, both are definitely standouts within their conventionality.
Lost Branch of Legend is very unashamedly copying the core structure of Slay the Spire, and unlike most deckbuilders, it does not try to evolve on that core in any bold ways. instead, it focuses on pushing the StS formula further, adding a more complex energy system, more complex cards, and some unique enemies. still, the addition of Touhou to the mix is enough to shore up a lot of StS's weaknesses (Lost Branch of Legend's art and music are both gorgeous, and the characters are fun) so it still brings something new.
The Witcher 3 is in many ways the epitome of the Open World Game, a genre that has dominated the AAA market for the last decade. the map is massive, there are so many sidequests, so many little map markers, so many caves, so much random environmental loot... this style of design holds very little appeal to me, and i avoid this genre like the plague. it's possible that Witcher 3 actually does innovate a lot here compared to its contemporaries... but even still, the Witcher stands out in its more dire world, its storylines that ripple through the entire game, and all the no-win decisions you have to make. the Witcher 3 really delves into the idea that there's rarely a "right" choice, in a way that makes it very memorable, even if the game is often very standard.
sorry!! to be honest, i'm having a hard time thinking of anything truly so conventional as to be forgettable that i've actually played. i have theories - my guess is that something like Horizon Zero Dawn would be really dull to me - but yea.
Ah, wait, maybe INSIDE is a good example? INSIDE had a couple cool moments and good visuals, but just really felt a lot like Limbo 2. the story struck me as pretty... generic. especially when compared to the more personal and harrowing writing of J.J. Macfield, INSIDE just kind of... feels... there...
ok that's my answer. sorry, INSIDE fans...

