I can say as an active dweller of the net, that I never had a problem with Firefox's speed to begin with. My gripes were always of a security-related nature, and that's coming from someone who isn't necessarily a security guru, just someone with a budding interest in opsec/infosec and a strong desire to tinker. From a usability perspective, Firefox was always above Icecat, Palemoon, or Tor Browser. Icecat's design can break most pages (As someone said further down, it has NEVER affected this site <3), Palemoon didn't seem as responsive, and Tor Browser is noticeably slower for reasons that are obvious to anyone who even knows a trivial amount about it. I've had to essentially compromise by hardening Firefox, using certain addons (NoScript, uBlock-Origin, Privacy Badger, HTTPS Everywhere, Disconnect, etc, while modifying a few options in about:config.

This didn't get rid of all of my concerns, but it gave me more security than what I was given out of the box. There was still the concern for sites like Youtube, but I found a program called Youtube-dl which allows you to use a wget-like download process by simply copying and pasting the link to the playlist or individual videos, which can then be watched in whatever specified quality/format you downloaded it in from your favorite media player. I've been told by other people that this seemed "paranoid", so I took it as not being paranoid enough and now sandbox Firefox, any torrenting programs, and VLC player with a program called Firejail. This solved a lot of my gripes with Firefox, and seems to give me as the best medium between security and usability..

For anything sensitive or personal I use Tor Browser. There seem to be plenty of criticisms for Tor, but it is also universally praised for what it can offer out of the box. In a perfect world, I2P would have the funding, political backing, and development power of Tor and then I would just use that for everything.

You could argue that being tracked is the only downside necessary. Depends entirely on the individual, whom they are supporting, etc in regards to whether or not the tracking part matters, but I would say you don't make it to this corner of the internet if it doesn't, right?

The success and development of one distribution isn't going to cripple the success of another distribution based on it with entirely different political and development goals. Devuan made the best choice they could in utilizing Debian as a base, which means that they can "leech" the user-base that used Debian, but wanted a more free and security-based distribution on the whole - they could then switch to Devuan. Personally for me, this was the case entirely. Debian seems more concerned with appealing to the general audience, often opting to bloat the distribution more than I need in order to appeal to a broader range of users, which isn't necessarily a bad move (if you don't mind double-backing on the more "ethical" approach to security or one's technical autonomy), it just cuts against some of my interests and desires. If there's a supply and there's a demand, there's little room for the failing of any project driven almost entirely by incentive and ethics.

The Dyne team are heavy-hitters and don't strike me at all as the type of people who build things that they aren't going to see through. They've literally churned out more creditable security-based projects than anyone out there, and every single project is highly regarded and respected in the various pools of individuals that float around in the multitude of privacy and opsec-related hubs. No one's a psychic, but I really don't see why anyone would have doubts about the legitimacy of a project like this. The world being as fucked as it is when it comes to the security and technical spaces almost guarantees Devuan's relevance; developers behind Devuan almost guarantee its excellence.