Can we make a faster Boole implementation?

The problem is the automatic module variable renaming that happens with With. You can use TracePrint to see this:

TracePrint[boole[list], _With]

With[{True\$=1,False\$=0},{True,True,False,True,False}]

{True, True, False, True, False}

One idea to circumvent this renaming is to use a pure function:

Clear[boole]
boole = Function[Developer`ToPackedArray @ With[{True = 1, False = 0}, #]];

Then:

boole[list]

{1, 1, 0, 1, 0}

See Using With to scope over pure functions, then try:

boole[list_] := With @@ Hold[{True = 1, False = 0}, list] // Developer`ToPackedArray

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