I played SMN since ARR, mained it for a bit in SB, and was fairly decent in 5.0 and actually disliked the egi assault GCD changes 5.1 brought personally. I have a bit of history with it.

People have wanted Egi's to be replaced with just big spells since ARR. Those little bastards have sucked in each iteration of the job. They sucked slightly less each expac, but they've always sucked.

The game lacked the proper mechanics for pets to be interesting, and frankly should have been removed a long time ago. Summoning for a big attack and augmenting your skills and changing how you play is a much healthier, sustainable, and honestly flavorful direction to take it. Ruin spam was boring. Dots had little to no thought behind them, especially when tri-disaster started refreshing itself during your rotation. The demis, while cool and letting the job feel like a summoner for some of it's rotation, had AI that broke all the time. The job worked awful with ping. So much of the job was just layer on layer of band-aid fixes on an outdated design that needed to have changed back when it came out.

That said, it was fun. I had fun with it despite it's jank. I do agree it sucks that people who managed to have fun with the older versions may not like the newer version. I personally do, but hey.

I think people are freaking out when it's not really needed. Summoner is now effectively a good base to actually build on. I can easily see 3 more summons taking the spot of ifrit/titan/garuda after phoenix, or maybe even something along the lines of the last summon buffing the next one in a unique way. It doesn't matter, but now they can actually do something instead of "well lets just add an entire new phase that doesn't interact with how the job worked at all prior because it's honestly just fundamentally flawed."

It sucks that it changed so much that you may not like it when you may have found it fun prior despite it's jank and awkward design, it really does. But we really should recognize this was specifically asked for since 2.0's launch. If anything, get hype because now an actual dot mage without stepping on summoner's toes.