Interesting question, I know. For me personally the answer is no - I have not ever regretted having gotten into bitcoin, despite having spent hundreds and hundreds of hours researching the topic. It's always been an interesting ride.
But I have a friend who got scammed and he regrets having had anything to do with crypto in the first place. It's pretty sad but there's nothing I can do about it. I even offered giving him half of the amount he lost from my own crypto stash (mind you I am not rich) but he's so scared that he's not interested any longer...
For me, NO, being on bitcoin is an opportunity for me, being in the community helped me in many different ways, well, I can't blame anyone for regretting more likely for those who invested on the peak of the coin, it's almost a year since the downtrend and losing value of coins is very disappointing.
I hope they won't lose hope from being here, things will work fine if they will stay here for long.