Of course that's true, but opportunity cost is not purely monetary.
They also need to consider the missed opportunity of building up a new franchise (or bringing back a returning franchise). Although such a game might have low sales in the short term, long term it may become a financially successful franchise. Compare this with the cost of bringing out a safe dudebro shooter that might sell decently initially but almost certainly will die in the long run.
Well I mean, they're going to pick whatever they think will sell best in both cases, right?
If you can get fairly high up on the dudebro shooter chain, that's a very valuable position.
Let's look at how Square Enix is spreading their bets for example:
Tomb Raider - Third person shooter market, uses an extremely well known brand. There are many successful shooters on the market, and this tries to go the somewhat less crowded Uncharted route.
Hitman - Present day assassination brand that attempts to "modernize" a successful series. Assassin's Creed is very successful and closest analog, but this is an alternative, differentiated attempt on getting in.
Thief - Potentially a much more direct assault on the Assassin's Creed brand. Has a known brand.
Sleeping Dogs - Undercover police angle on the successful sandbox-GTA genre. New brand, but Square Enix didn't have any useful brands in this arena.
Just Cause - Over world genre. Tries to capitalize on the explosion/vehicle heavy open world market that was once successful with Mercenaries.
Deus Ex - Hub based RPG, not many analogs, but it is quite a well known brand that had pretty good sales so they're trying to forge ahead as is.
IO's New IP - Seemingly a replacement for Kane & Lynch. Entry attempt into the co-op third person shooter genre.
Final Fantasy - Flagship international JRPG brand.
Dragon Quest - Flagship Japanese-centric JRPG brand.
Kingdom Hearts - Formerly a flagship Japanese action RPG brand that tied in heavily to the successful Disney megabrand.
They're pretty much doing what would make sense when starting with a base of extremely few active, successful brands.
Namely they're taking 1-2 stabs at each given genre - some differentiated, some not as much - and seeing what works and what doesn't.