I wasn’t careful enough with my analysis of CuraLE 3.7.18. The prime tower does, in fact, print each color in a separate X,Y location so it does indeed print color 2 in thin air (move the “camera” view to top down). This is obviously a bug and I’m not sure when it was introduced as I have successfully printed dual colors in previous versions of CuraLE. I need to do more research and then I will submit a bug report. I’m not sure if the process for submitting a bug report is documented anywhere (it should be) but I’m willing to bet that an email to email@example.com will be an adequate substitute.
FWIW, Ultimaker Cura 4.2.1 appears to have the same problem. Simplify 3D (S3D) does not have this issue. You asked if S3D is worth the money and my answer would be yes in this case as it does the prime tower correctly. There are some features in S3D I like better and some features in CuraLE I like better. I’d say that 90% (or more) of my printing has been sliced with CuraLE. For LulzBot printers, S3D will require some tinkering (and more tinkering if you use OctoPrint).
I like to experiment and have found that having multiple slicers in my toolbox can sometimes allow me to match a slicer feature to a model and get a better print.
There are other slicers (PrusaSlicer, KISSlicer, IceSL, Pathio) that might work but you will have to create a printer profile.
KISSlicer is free for a single extruder, but you have to pay for multiple extruder support.
IceSL and Pathio are both being developed and are currently beta releases. IceSL does not have support for the LulzBot TAZ6 Dual Extruder V3 yet. I submitted the LulzBot TAZ6 Single Extruder profile but the Dual Extruder is still a work in progress. Pathio has dual extruder support but I haven’t printed anything with my dual extruder yet.