Having basically mained SMN for this current tier and played older iterations of SMN, my opinion is mixed.

On one hand, this new SMN feels a lot closer to older FF where the summons are called down, do burst damage and leave. This SMN is no doubt how they want to take it going forward, having three staple summons and then rotating demi-summons. I do like this as it feels cohesive instead of a dot/pet mage. SMN never has been a dot mage in any Final Fantasy game and we all know how they feel about pets.

On the other hand, 6.0 SMN lacks a lot of complexity. Energy Drain/Aetherflow feels like a leftover and boring filler. Utility attached to demi-summons feel pointless as you're never going to hold Phoenix for the regens. Carbuncle is just a placeholder for other summons.

However, I do believe that they changed SMN for the better and the health of the job. They have a new template to work with. No hate to the people who enjoyed old SMN. There were more decisions involved and a lot more complexity to it. But the job was heavily disconnected. Dots have nothing to do with summons and the pet ai was atrocious. Pretty much in any MMO concerning summoners, the pets are glorified turrets. There was just far too much spread out and it just makes the job feel so disjointed.

I would like to see utility moved from demi-summons to mini-summons that are oGCD, like summon Moogle gives the party an AoE regen, Ramuh/Sophia causing a dot, Alexander to give a ST regen, Shiva for Painflare damage, etc. That way you there's filler that feels connected to the job fantasy. You're using big damage summons, but also summoning small versions of other primals to assist you.

Like someone else said, I believe SMN will never have a happy fanbase because people become attached to older versions (kind of like how AST mains go back and forth on card system).