> The statute doesn’t say anything about “dual intent.”
V, L and H-1 (including H-1b, but excluding H-1b1) nonimmigrant visas are explicitly, by statute, excluded from the rule requiring nonimmigrant visa holders to lack immigrant intent; Immigration and Nationality Act Sec. 214(b), as amended, codified at US Code Title 8, Sec. 1184(b).
"Dual intent" isn't an administrative fiction, its a term of art for the nonimmigrant visa categories excluded from the generally applicable requirement for having (and demonstrating) the absence of immigrant intent. Its true that there are some visa categories where "dual intent" is applied adminstratively rather than from a clear statutory rule, but V, L, and H-1 (except H-1b1) visas have explicit statutory allowance for dual intent.
> If Congress had designed H-1B to be a pathway to permanent residency, it would say that in the statute.
But...it does say that in the statute.
> Instead what happened is that for 40 years the executive branch abused the H-1 program to turn a temporary immigration visa into a de facto permanent immigration system.
Whether or not H-1 may have been abused that way between 1980 and 1990 (the first 10 years of your "40 year period") [See EDIT below], the exemption of H-1 and L visas from the no-immigration-intent requirement has been express in statute since the Immigration Act of 1990, so for the last 30 years the behavior you complain about has been strictly as directed by statute.
References:
Summary: http://www.americanlaw.com/dintent.html
Current codification and history: https://www.law.cornell.edu/uscode/text/8/1184 [history of amendments, including text added by the 1990 amendment at issue, by clicking "Notes"]
[EDIT: The H-1B can't have been abused between 1980 and 1990, while I checked when the H-1B was added to the exception from the no-immigration-intent rule, I didn't check when the visa category itself as added, which was at the same time in the INA of 1990. So, no, it was never abused as a route to immigration, it has always explicitly allowed that use in the statute. Conceivably, the unsplit H-1 could have been abused between 1980 and 1990, though.]