MGS1 isn't a difficult game, though. The control scheme is less complicated than any other game in the series, and it's designed around what limitations it has - not be able to aim in the first-person, hang over ledges, rolling, etc. Guns have auto-aim kick in when you're in range of someone, guards have stricter paths and can't hear noises unless you're on grating, cameras can't be destroyed but can be disabled.
The problem isn't that the MGS2 mechanics are bad, necessarily, but that the level design and AI weren't updated, and adjusted, to accommodate them. The result being a broken mess of an experience, making it much less enjoyable as a whole, provided you're into MGS's brand of gameplay.
MGS1 was a simple but intelligently designed game; TTS takes that and warps it into something else entirely. It wants to be MGS1, but it really isn't anymore. It's just not a very good remake, or game, and it stands out against every other MGS. If nothing else, it's a good example of why you don't let a C-tier developer handle a major series! Fortunately, Konami wants to remake MGS1, so at least there will be a modern version done right out there, hopefully.
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Simplicity is the ultimate sophistication.