If you look at the EO list that I linked to for Trump's 2017 EOs, they were almost all about implementing laws within the executive departments. He wasn't "making law" with his EOs, which is why I'm a bit confused when you say "This would have largely avoided ruling by fiat EO." I'd need you to show me an EO that Trump "ruled with" that was rightly in the domain of Congress that supports the missed opportunity to "build consensus and pass conservative legislation." I think that both can be done in parallel: EO's are about implementing existing law within the executive departments and working with Congress is about passing new laws.
To my latter point, there is the question of whether new laws are necessary if/or existing laws are already on the books that can be enforced?
The 115th Congress (2017-2019) gave Republicans a 52-48 majority in the Senate, which is not enough for cloture without Democrat support.
In the week before Donald Trump took office, the Senate began the process of repealing Obamacare via the budget reconciliation process with a 51-48 vote to proceed (Rand Paul joined with the Democrats in opposition).
In February 2017, VP Pence had to break a tie on a confirmation vote to appoint Betsy DeVos as Secretary of Education. Joining the Democrats in opposition were Susan Collins (ME) and Lisa Murkowski (AK). This was a foreshadowing of the nature of the Senate that Trump would be facing.
In April 2017, Senate Republicans invoked the "nuclear option" to remove filibustering of Supreme Court nominees in order to confirm Neil Gorsuch. This move hardened Democrats against President Trump.
In June 2017, Steve Scalise was shot.
In September, the Senate Parliamentarian gave the Senate until the end of the month to pass Obamacare repeal via reconciliation. This would be infuriating to Democrats and making them unwilling to participate in furthering Trump's agenda.
In October, the "Me Too" movement began and resulted in the resignation of Al Franken (D-MN) in the Senate and Tim Murphy (R-PA) in the House. Trump was acccused of raping or molesting 19 women and Sens. Kristen Gillibrand (D-NY) and Ron Wyden (D-OR) both called on Trump to resign. Sens. Cory Booker (D-NJ) and Jeff Merkley (D-OR) joined them a few days later.
It was in this hostile Congress that Trump was able to pass his 2017 tax cuts that lowered the corporate tax rate, doubled the standard deduction, reduced the limit on State and Local Income deductions to $10,000, and repealed the tax fine for violated the Obamacare mandate.
However, the Obamacare repeal via reconciliation was blocked in the Senate by Susan Collins, Lisa Murkowski, and John McCain who all joined the Democrats to defeat the bill by a 49-51 vote. McCain gave his famous "thumbs up" after voting NAY on the bill.
I would have loved to see President Trump have a supportive Congress at his back, but I believe that personal politics in the Senate got in the way and Trump was lucky to get through what he did (one Supreme Court Justice and major tax cuts).
2018 brought us the Brett Kavanaugh confirmation that began in July 2018 and dragged out through October 6 2018 when Kavanaugh was confirmed by a vote of 50-48, with Republican Steve Daines absent for his daughter's wedding, Lisa Murkowski agreeing to vote "present" to cover Daines' absence, and Joe Manchin (D-WV) voting with Republicans to confirm.
I seriously don't know what President Trump could have done differently to work with this Congress after the confirmations of DeVos, Gorsuch and Kavanaugh, and the passing of his tax cuts, all while Democrats were smelling blood as the Russia Hoax was building steam (with John McCain working with the Democrats to take down Trump).
-PJ
Your very detailed reply is much appreciated. Many thanks for your time and efforts. You surely have earned your screen name.