Since the original topic title is "Moving back to extract brewing", let's drift back that direction...
The "Texas Two Step" method seemed to have disappeared from the free portion of the internet. IIRC, it can be found in one of Chris Colby's books. The idea is to brew half the beer in the 1st batch, half in the second, and merge batches in the fermenter. In some situations, it has advantages over 'partial boil with late additions of extract & water'.
"Extract twang" is most likely stale LME. It may also be related to bad process/technique.
"Homebrew taste" most likely due to bad process/technique but could also be a bad recipe (overly mineralized wort) or perhaps slightly stale LME.
"Color": DME can deliver color toward the lower end of a style's range. Yes, it's not as light as "all-grain". So "darker than expected" is most likely bad color estimates. If it's a kit, it may be due to not re-estimating color after converting the recipe. Boiling "too hard" may also be a consideration.
"Brewers crystals" are a product that can be used to manage color (and mineral content). I gave up talking about it as the price per pound varies wildly between online stores. The stores that I use stock it at a price per pound that's equivalent to that stores DME ($9.50 for 3# bags).
Rice solids are a similar product.
How to create an "overly mineralized" wort; as an extreme example) imagine (because it doesn't exist at this level) a DME product with 50 ppm Na (Sodium) at OG 33. Make a OG 100 wort by using 3x the DME. The Na in the wort will be 3x as well (150 ppm).
For those who want to exBEERiment: Make a one gal OG 88 beer (your choice of style). For DME products, in addition to Briess: Home Brew Ohio (HomeBrew
Talk sponsor) stocks Muntons DME; Williams Brewing (HomeBrew
Talk sponsor) has a 3rd brand of DME that I have not tried; and MoreBeer's "flash brewing" DME is stated (by MoreBeer) to be different from other DME products.
Putting it all together ...
With DME, I brew 2.5 gal full volume batches in the kitchen (induction cooktop). With DME, it's shorter boils (max of 30 minutes) with a soft boil (
Boiling Wort Visual Reference). I typically add sugar, brewers crystals, and DME at around 160F as I'm heating to a boil. The order is important as I can visually see if the sugar and brewers crystals have disolved or are stuck on the bottom of the kettle.
In the "I brewed a favorite recipe today" topic, OP describes how to disolve DME in a side dish when working with late additions of DME. I found that this technique works slighly better for Muntons that for Briess - but given some time (say 15 to 30 minutes) it works for either product.
and finally ...
A topic here at HomeBrewTalk to consider "AHA homebrewer of the year": he won with an extract based American Lager.
https://www.homebrewtalk.com/threads/aha-homebrewer-of-the-year.695096/