I'm thinking that Atomic Knight likely has more rant coming, but I can relate.
I started my action figure collecting in around 2000 when I was 25 and my first son was born and was ending my "party days" of going out all the time. I started collecting the Toy Biz 6" Marvel Legends and their various "Classics" and movie sister lines. I also started buying DC Direct around that same time. Marvel has always been my #1 and DC my #2 interest when it comes to figures. My favorite IP is X-Men followed by a second tier of Batman, Spider-Man, Avengers and Justice League and then several others IPs like Fantastic Four, Superman, Wolverine, etc. on lower tiers.
I collected everything DCD in those early days and I loved the more obscure stuff such as Vandal Savage, Tom Strong, Promethea, Sandman and the Endless, The Authority, Planetary, Preacher, Promethea, Phantom Lady, Legion of Super Heroes, etc. When Mattel announced their DCUC line, I slowly began replacing my DCD figures with Mattel substitutes but keeping the DCD stuff that Mattel didn't make . I remember even then getting frustrated because many of the DCD figures I hung onto were too tall to properly mix in with the Mattel stuff. The difference in articulation didn't bother me as much as the scale. I still continued to buy DCD figures (renamed DCC) for characters that Mattel didn't make and the newer DCC stuff seemed to blend in with the Mattel stuff much better than the older stuff did. I was mostly happy even if I didn't like my DC collection as much as my Marvel collection that continued from Toy Biz to Hasbro at the same basic scale.
Then came the announcement that the DC license was moving from Mattel to McFarlane. At first I just shrugged. I had owned lots of McFarlane Spawn figures but felt the early stuff was mostly cheap junk and the newer stuff at that time were mostly just intricate statues with little to no articulation. That had been my prior experience with McF. Then came the news that they were changing the scale to 7" and I was beyond livid. I swore that I was done and that I was out. Then I got pulled in with buying some of the "Dark Knights Metal" stuff that neither Mattel or DCC had gotten to. Then I started finding a lot of McF product for deep discounts of 50% or more at retail in those early days when he was over-producing and I started buying more at those clearance prices. Fast forward and now I'm at a point where I have at least one version of every character that McF has done in the line.
I have a lot of McF figures that I do really love, but I've still honestly never really "bought in" and still consider my Mattel stuff to be the core of my DC Collection. I've never sold any of those figures. I fully expect to sell most, but certainly not all of my McF collection as we move forward with Mattel. I'll keep all of those characters that McF has done that haven't been done by Mattel or DCD but everything else will likely go over time. I'll likely keep all the vehicles from McF though as well as I've bought every single one. I expect that the new Mattel line will eventually become my core DC collection, but I'm withholding judgement on that until we actually see the product. I still like the old Mattel MOTUC more than I do the new Mattel Masterverse, for example. I'll likely avoid the basic low price point figures and only focus primaily on the "Ultimate" and some "Elite" collector stuff (if they follow the WWE model). My focus will continue to be on figures of characters that I don't already have in my collection from the last 25 years of collecting DCD/DCC, Mattel and McF and only upgrading when appropriate.
While I'm not as big of a DC fan as I am Marvel, it irks me that the various companies haven't been able to stick to a consistent scale. I expect differences in paint and articulation across different manufacturers, but I really wish that all 3 companies could have kept more consistency with scale. If Mattel is really now doing 6.5" instead of 6" as rumored then it feels like they're trying to "split the difference" and I'm not particularly crazy about that idea either. It will depend upon the execution, which remains to be seen.