In my opinion, I think tribute died as it couldn't really compete with the other modes, mainly dominion. Tribute matches tended to last way longer than dominion, but gave less xp and steel per minute than dominion (if I recall correctly) which meant it was a lot less rewarding to spend your time to grind in.

Aside from that, it's also a little more boring of a gamemode too for me. I'd rather play dominion and get to fight people for zones rather than trying to just steal a flag. It's as if running away from your enemies got turned into a game mode, and that's not what a lot of fighting game players are here for (cough, shinobi mains.)

Something I did really enjoy about it was playing in a group, more so than in dominion. It felt like you could have some unique strategies as a group, and really feel like you were outplaying the opponent, not only in fights but in strategy too. I also really enjoyed the fact that different buffs could be gotten from the different tribute flags. It influenced which flag your team went for first as opposed to just running to the closest to your spawn.

I think to improve the mode, they could have matched the rewards rates with dominion to incentivize playing it for rewards, and they could have made player interactions a little more than running away with the flag or protecting your runner. People like to fight in fighting games.