ALL BRONIES GET TRIGGERED OVER CHANGES LIKE TWILICORN, EG, FLURRY HEART AND STARLIGHT AND THORAX AND THE CASTLE AND ETC.

The only one of those you named that I genuinely hated was Thorax in the season 6 finale. It's not necessarily the design or any of that, it's what he did. In one episode, he and Starlight:
-nearly committed regicide
-absolutely committed genocide (as far as we know, the old changelings, aside from Chrysalis, are non-existent anymore)
-caused the show to have (gasp) a reoccurring villain!!! (honestly, that's the one change from Thorax I enjoyed)
-caused an entire kingdom to revolt against their queen (in literally any other scenario, this would be punishable by mass execution. it's unrealistic and makes no sense, considering their loyalty before hand)
other than that, I'm pretty "meh" about the changes. I learn to tolerate them, but Thorax's heinous actions are INTOLERABLE! No wonder Chrysalis saw him as a traitor. HE IS A TRAITOR AT THE HIGHEST PERCENTILE.

ahem, sorry... had to get that out of my system...

...although I'm not without my personal moments...

actually, i loved all of them! before season 4 came out, Magical Mystery Cure was my favorite episode of the entire series! and the new look of the changelings is very pretty. and also the castle is a really important part of the series because of the cutie map!

and also Flurry Heart is a really cute baby alicorn. and if you have seen the third episode of season 7, she didn't actually mean to hurt anyone, she just wanted Twilight to play with her!