“But the modern Orthodox Jews have found modern ways of stretching and shrinking the latitude of their own rules, rather conveniently it seems.”
They certainly do,like the eruv.
.
So whose eruv do you hold by, Rabbi?
(save you the time - eruv has been around in Jewish text for at least 2600 years).
The concept of the eruv is millennia old, dates at least to the Babylonian exile. Over the centuries rules have been reinterpreted as larger urban areas developed and construction methods changed.