Why aren't you riding the Sejuani gravy train?

I can't take any of your points seriously because you're using the word feel which is subjective so I guess I'm gonna have to make an assumption on why you 'feel' that she is easy / 'autopilot' even though she is overall more difficult to play than before.

Old Sejuani skill rotation excluding ult was Q in, W off CD and E off CD. New Sejuani is pretty much the same except W requires more skill rather than just being in melee range. E also requires more skill, rather than just mash after W, although the skill difference is pretty negligible it's there. You also have to use a spell or auto attack on the person you manage to land E on in order to maximize her stuff which is more skill.

I understand how you might feel skillfull landing a 'game changing' Sejuani ultimate and now you don't 'feel' good for using her ultimate but how much skill was there in the first place. Basically the most successful Sejuani ultimate requires the following, this is excluding team mates. Near melee range, as the ultimate is a pretty far projectile hitting it from range seems like a good choice. However when you do this you're wasting time gapclosing and reducing the effective duration of the stun from 1.75s to ~0.75s. So ideally you want to be landing her ultimate in melee range, not only because it's more effective in getting off damage but also because it's more reliable as people can't dodge it. So overall the most optimized
(I imagine proper optimization also makes you 'feel' skillful) way to use Sejuani ultimate is to go in melee range and point blank it. Aside from hopefully getting a big stun her ultimate served no other purpose.

I'm going to repeat what I said before now...

New R has more skill in place in order to get the 4s CC lock combo. You have to land W or auto attacks, then you have to position to land R and also time the 2s so you don't overlap the stun duration. The best usage of old R was to get decently close so you're not wasting the stun duration and land it so you can follow up right away. In other words when you see them bunched Q and R. New R needs to be cast from a moderate range in order to actually be an ultimate ability.

New ult can be used in different ways outside of stunning due to it's new mechanics. You can now use the ult to combo as you said or zone or start teamfights. An ult that lands in the middle of a team and ideally stuns a squishy target is still a good ult. It forces the enemy to move out the way or get 80% slowed and take a good burst of damage. Old ult you just cast without any thought, now you have some decision making between comboing, starting a fight, zoning.

Now you could say "hey can't old Sejuani ult pretty much be a zone tool", yeah it could but no where near as good as this new one. When both ultimates are used as zone tools the old one lacks as the team has the option to stay apart during the cast. Due to the slow field it means you don't just have to aim for champions but also areas.

So going back to my main point, she does have more skill expression now which is completely unrelated to 'feeling easy' btw. After deciphering your 'feelings' I can agree that she still is pretty auto pilot but absolutely more difficult. Her ultimate has more uses now so it isn't auto pilot.

I also don't think Sejuani is 100% pick ban freelo either. If you want to hear more of my reasoning you can ask cause this starting to tangent off my main point.