I've played Resto Druid since Vanilla. In vanilla and the earlier expansions there used to be Spirit on gear, and there was also MP5 at one point. Some rare pieces even had Spirit AND MP5 on it. While some healers would gear for throughput, I would always gear for regen as much as absolutely possible (Dual Solace of the Fallen trinkets, etc). I would basically keep Lifebloom up on the tanks while spamming my most expensive spell (Regrowth) on the raid as much as possible. It was a much more simple style of healing compared to how I heal now, but it had a strong appeal at the time since it involved casting spells basically as fast as I could throughout the entire fight with almost no regard for mana, and I was able to do a TON of healing. I had a program to measure how many times I clicked my mouse and I actually clicked my mouse over 30,000 times in a single raid night at one point. I would wear out the buttons in my mouse in about 6 months.
It was a difficult adjustment for me when they got rid of mana regen as a stat (Spirit and MP5 removed as stats), and made it so that you could not gear for regen aside from a few oddball trinkets here and there. I hated feeling like I was being forced to heal in a totally different way than I had before (a much more significant change compared to normal expansion changes), and this was the closest I've ever come to quitting the game.
But ultimately I stuck with it and in the end it probably made me a better healer overall. I actually learned how to properly factor mana efficiency into my healing, and make better use of my entire healing toolkit. If I remove nostalgia from the equation, then I guess I have to admit that it's better the way things are now. But there will always be a part of me that misses that infinite-mana, spam heals until your fingers stop working style of play. Of course I'm older now, I'd probably get carpal tunnel syndrome or something trying to play like that now.