That kind of stealth gameplay certainly didn't detract from Thief's gameplay.
Yes, because the entire model of stealth in Thief is completely different. The person asking the question wasn't asking for Thief's stealth, just to remove DX:HR's 3rd person view. Since DX:HR's stealth is based on sound and (more importantly) line of sight, not light levels, this would be catastrophically bad.
In Thief, their equivalent to being able to peer around corners was being able to observe from darkness. Most corners and approaches were darkened to allow players to move to a position from which they could observe guard patterns with effectively no fear of detection. Much like Deus Ex and Splinter Cell and various other games with good stealth mechanics, the guards follow extremely regular patrol patterns so players can patiently memorize them and either evade or stalk their way forward.
"Realistically" I doubt the residents of the City all love living in buildings that are so dark that you can navigate most hallways without being able to see a human being crouching 2' from you, and in which there are amazingly consistent shadow paths through which a talented thief can pass undetected, but these are understandable conventions for the type of gameplay the designers were trying to produce.