I'm sure if Mashima pressured Kodansha to promote FT they would do it, he might even do it himself, maybe doing color pages more often, but he doesn't do it either, neither Mashima nor Kodansha seems to have any interest in promoting the series. I don't know if EZ will gain momentum (it seems unlikely, it had a better chance to stand out in its first season, since it only competed with BNH and TR) but it doesn't really matter, the annoying thing is still how little attention Mashima gives to YQ100. I think there are many readers who only follow Mashima through FT, they may support the mangaka by reading his other works, but if in the end you make them choose between him and FT, they will surely choose FT (The difference in sales of EZ and YQ100 is proof of it).
I don't know what weight Mashima is placing in the series, it seems that whenever he has time, he prefers to be in another project than in YQ100 (new original anime on the way, new manga on the way, Gates manga, spin-off of series, he helps in the art of video games and other series) and when appearing he always tries to get a new job before dedicating himself to YQ100, I understand that his priority is EZ, but he just announced the end of this series and already wants to start a new story? so YQ100 is not even the second priority of him? in fact YQ100 has any priority in the life of him? it seems he only does it because he gets a check at the end of the month.
If the only thing that stands out from Mashima's works are his designs and Ueda now does this for YQ100 then it's clear that Ueda is going to get more recognition than him, I mean, it's not like Mashima is trying hard to tell a story (despite that at the beginning of the series he said that he had a plan and a story to tell [I think his plan was to keep improvising]), I think if Mashima is somehow upset that Ueda gets more recognition, then he should take the series on its entirety rather than planning a new series after EZ.
I have never said that EZ harms the sequel, but what you say about Mashima's time, it is something that he himself wants, I understand that a mangaka can get tired of writing the same story for 15 years, but then let it go, Mashima seems a small child who, when another child arrives to use a toy that he does not like, immediately becomes jealous and takes it away, but once he leaves, he leaves it forgotten. If mashima is tired of YQ100, then let him leave history, surely someone else can continue writing the same mediocrity that he does.
The anime has been in production for about 2 years, if A1 is in charge then at least I hope to see something like Dragon Cry, the fight with Animus was quite good and the designs of Lucy with her star dress were great, although of course I prefer KyoAni although it seems unrealistic.