Working for Big 4 Firms is definitely a great experience provided you are willing to work hard. If you’re not don’t sign up. The people that you work with are definitely what sealed the deal for me.
Like any larger organization, you will have strong performers and some less so. The best way to navigate this is by making sure that your Partner is one of the high-performing ones and learning from... them. At the end of the day, a Big 4 Is not for people to slack off, work nine to five, or go home every night (due to travel). As long as you understand that you have the potential to have a great experience.
One of the best Big 4 in terms of flexibility when I was interning, actually committed to hybrid. Training at Lakehouse was great fun and my team always helped with specific instructions afterwards.
The kind of work you do as an intern isn't always the most interesting. The real grunt work is outsourced but unless you actively talk with your manager that you'd be interested in doing better work... you risk getting stuck with whatever is leftover.