Hard disagree there, the game is every bit as complex, polished, and varied mechanically as any Japanese game.
The issue isn't mechanics. If there's any failing at all I will grant you to TLOU it's that the mechanics don't substantially change over the course of a rather long campaign. The encounter at the courthouse or crooked building near the beginning of the game is functionally almost identical to the hospital or preceding sewer section at the end of the game; imo, that's a failing more of enemy variety than anything else: Human enemies are largely the same throughout the game and the infected are typically the same collection of zombies and clickers throughout most of the game, and on easy and normal difficulty lurkers and bloaters are hardly used at all. Which makes the encounter design somewhat one note, particularly if you're not playing a harder difficulty. I have hope that with things like the dogs they've shown in TLOU2 that the encounter design will hopefully be punched up.
What you're describing is essentially the same for most TPS out there, including Resident Evil, Gears of War, Ghost Recon, Dead space, Red Dead Redemption etc.
If anything TLOU actually still offers
more gameplay diversity and encounter complexity than most, by way of the fact that it has a combination of gunplay, dynamic melee, stealth, use of environmental objects as well as on the fly in gameplay dynamic crafting (something that is unique to TLOU).
In terms of controls, movement fluidity, AI and level design, on the whole it's also stronger than many contemporaries, including vs Resident Evil, hence enemy variety only really tells a portion of the story.
Ultimately whilst comparatives like RE4/RE2R as two examples (that I love/enjoyed), may have better enemy variety than TLOU, the fundamental combat gameplay doesn't really change much over the course of those games either, and in terms of combat gameplay, in some ways they're far less nuanced, diverse and sophisticated in RE (due to tank like restrictive movement and controls, lack of stealth and cover mechanics, limited melee and environmental interaction, really poor AI, lots of mechanically basic slow stop and pop corridor funnelling style combat scenarios and so on) compared to TLOU.
