Every element/monster has the potential to be used well or poorly and this is down to the architect. It therefore doesn't make sense to assume that just because a level or room has tar in it that it will be less fun, or tedious, or bad.
Tar, used well, can be used for interesting
tar cutting puzzles, as a timer, for limiting player movement in a particular directions but not others (e.g. to make a maze), for generating tar babies for use elsewhere in a puzzle, in order to manipulate other elements (e.g blocking their movement) etc etc.
Used poorly it can obscure other elements (hiding walls or trapdoors underneath is very annoying), used for hack-and-slash (e.g. generating tons of tar babies every 30 turns), or used for a tedious slog through tons of tar with multiple tar mothers.
The same applies for the use of snakes, stalwarts, briar, whatever and obviously the delineation between the two categories will vary between architects and players.
KDD was the very first level set ever so there hadn't been the opportunity to make this refinement to see which puzzle types worked or didn't. In my opinion, it's not the greatest introduction to DROD. (Some of these issues are improved upon in the Flash version however).
Don't get me wrong - it is not bad, given that it was the first hold ever, and it does have its good parts, however you may be better off looking at other holds to get more out of DROD.
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