In some ways, yes, limited inventories are to prevent the player from making the wrong choice but it is also a point to ask the player do you take X or Y, and having a choice between those two options makes the player choose a playstyle. Of course, you can absolutely still do this without a limited inventory. Deus Ex does it right at the start of the game where Paul runs up to you and gives you 3 weapon options and straight up asks how are you going to play this game. That said it's supposed to be a reminder, a constant active choice, on what the player is picking for their playstyle. That said...

Honestly, you've kind of swayed me more into wanting unlimited inventories. You are right, limited inventories seem to be a design crutch used by a lot of games that don't think of their whole ramification and more important the actions needed during other gameplay to justify a limited inventory. I will say I do think certain games make a lot of sense to have limited inventories but I would really like to see designers move away from limited inventories to allow more player freedom. I could see taking Doom 2016's style of driving players toward getting more resources while keeping inventories unlimited (and not putting you in a gameplay-breaking cutscene).

Unlimited inventories certainly work really well for the latest Hitman series which kind of shows that it could have worked for Deus Ex. In fact, in the first half of the Deus Ex, you work for UNATCO and could just let players collect a bunch of crap and then have them turn it into the evidence locker or whatnot. The design choice to simply limit your inventory can be seen as almost lazy nowadays because it means no one is thinking of what happens if you don't have a limited inventory. It's certainly given me a lot to think about on how I'd build or design a game without the inventory limitations.