Unfortunately, during the transition to quantum and WebExtensions the developers blocked add-ons making changes to the Firefox interface, which crippled TMP and a variety of other add-ons. To suddenly have your favorite add-on crippled is a little painful but what made me walk away was the tone of responses from Mozilla people on the boards and the bug reports. It ranged from dismissive, to arrogant, to angry which, particularly given how quickly the transition took place, just added insult to injury.
It seemed like Mozilla did get the message by the end of 2017 that their approach and response to add-ons had alienated many users. One of their 2018 visions included a statement that 'In 2018, extensions will be one of the reasons why people choose and use Firefox.' Unfortunately, when I looked at the TMP message boards last year I still saw very little in the way of signs of cooperation and encouragement from Mozilla. The TMP developer, onemen, still seems to be trying his best to produce a suite of extensions to reproduce the lost functionality and to be fair to Mozilla they have been moving obstacles out of the way but the pace is glacial.
Chrome may be creepy and invasive but right now it's far more flexible and remains a smoother experience. I'd really love to switch away from Chrome but I won't trade it for an inflexible Firefox UI. If Mozilla could loosen up on the UI restrictions, demonstrate that they're doing everything possible to make the product friendly for add-on developers, and somehow get themselves around to replicating, or helping to replicate, TMP and other crippled add-ons then I would enthusiastically consider switching.