Same here. Tab mix plus (for multiple tab rows) is the reason I kept using FF all these years. WebExtensions does not provide the capability to manipulate tabs the way TMP did.
JS-based (crippled IMHO) vertical tabs are also in Chrome. Why would someone switch from Chrome to Firefox to use a crippled extension?
I hope I am wrong but I don't think Firefox will be able to increase their market share. They may be able to stop losing their market share, which is not really a huge achievement.
Crippled? Sorry, I don’t get what you’re trying to say. Tree style tabs work fine in FF57. Only annoyance is that the top tab line cannot be removed. That’s supposedly coming soon though.