If WW2 trench warfare really was a poor use of outdated tactics then what what would have been more appropriate tactics to employ?

Take any unsolved problem in mathematics; attempt to solve it by substituting 1 for the first variable, 2 for the second, etc. (solve through exhaustion). It is easy to demonstrate that any given solution is wrong. But the wrong answers don't really give any useful information about the right answers.

Policy (strategy/tactics/operations/etc.) is similar, but worse. There is a solution to most mathematical problems. Policy problems have a higher proportion of wicked problems where there is no clear mechanism to judge whether a given solution is right or wrong. Some solutions are clearly wrong [King Otto of Happy Valley][3]. But comparing two solutions requires a judging function and the stakeholder may not agree on the judging function. Some people are willing to trade lives for land; others are willing to trade land for lives. Almost everyone will have a different preference/utility curve between the two. Then add more options - what if we have to compare different solutions with different combinations of lives, land, time, money/resources, etc.

was WW2 trench warfare really as poor a tactical (and/or strategic) way of fighting as I often hear implied?

How do you define "poor"?

Presuming the answer to 1 was yes then what was the better approach everyone failed to recognize?

What makes you think that there is an optimal solution, or that understanding a single suboptimal approach will give any guidance to an optimal solution?

[3]: https://montypython.fandom.com/wiki/The_Tale_of_Happy_Valley_(The_Princess_with_the_Wooden_Teeth)#:~:text=It%20was%20ruled%20by%20a,had%20died%20on%20February%205th).

Answers:

Question 1: NO, trench warfare was not a "stupid way of war" in WW2 Question 2 and 3: No need to ask this way because 1's answer is no

Details:

There are a few misconceptions in your question:

• Trench warfare in WW2: Trench warfare was not a widely taken solution during WW2. When it was used, it was generally a correct decision. Some examples: Russian defense at Kursk, German defense in Normandy
• The quote you gave looks to me close to the sort of critic addressed to WW1 generals, not WW2. I think you're confusing the two conflicts in your question
• The technology you mention is not linked to "trench warfare in WW2". I mean it did not appear with its full potential by that time: Machine guns appear with their full potential during WW1, and their appearance was one of the reason for which trench warfare was widely used during WW1. Gas was a tried solution during WW1 for getting out of trench warfare, and most of the time it was not enough. It was rarely (I think never) used during WW2. Tanks were one of the solution used to "go out" of trench warfare during WW1. It was part of the solution leading to success of the Allies in WW1.

Arguing that this or that tactic is appropriate or inappropriate always depends on the context, not just on the date.

In WWI, the Western front had a density of troops which, combined with machine guns, magazine rifles, and artillery, made some sort of trench warfare necessary. WWI started out with maneuver warfare in the West, not just in the East, until forces got mobilized in such numbers that there just wasn't any gap left to maneuver through. During the war, technical and tactical innovation greatly changed trench warfare -- numbers of trench lines, positions of reserves, command and control, artillery, tactics to attack. The Eastern front of WWI was quite different.

In WWII, one might very generally say that combined arms tactics had advanced beyond the late WWI standard. Early in WWII, the German Blitzkrieg tactics combined tank-heavy formations with weak motorized infantry, artillery, and engineers, plus close air support to make up for artillery deficiencies. Behind those spearheads, the Wehrmacht walked next to their horse-drawn artillery and supply wagons.

Later in WWII, all sides understood that more, and better equipped, armored infantry was required to go with the tanks. Thanks to American industry, the Western Allies could make it happen to a much greater degree than others. But it also mattered that they did fight in Western Europe, where logistics were good. They were in Burma and the South-West Pacific, too, where they fought with more foot-infantry-based troops.

Again generally speaking, defensive tactics cannot win wars. But they can be an economy of force role, allowing small forces to attrit larger ones. Meanwhile, other forces are held for the offensive, either elsewhere or at a different time.

So it might make sense to dig trenches. The French Maginot Line got a bad reputation because the French lost in 1940, but in a way it did what it was supposed to do. French and German mobile forces concentrated in different sectors, and fought there.

And if the enemy has fortifications (either peacetime forts or newly dug trenches), the other side can either decide to fight elsewhere or accept the losses of a frontal attack. A well-sited fortification is not easy to outflank. The Germans went through the Ardennes because the Allies did not expect them there.

In summary, any general in WWII should have understood that it is a bad idea to storm well defended trenches with human wave attacks. Much smarter to outflank them, or to use a force including tanks and artillery. Unless there are no mechanized forces, or there is no time.