Being in a mundane job and checking out at 5 has it's benefits - you have both the time and the energy to focus on the projects and people you actually care outside of work hours. You also don't have to worry about money.
Your instincts may push you into a small startup where your work has immediate impact and feedback, but there's a space between 10 employees at 100K employees. I used to be in consulting (at a software company) and I worked with everybody from small startups that wanted to partner to companies with 200K+ employees. I tended to enjoy working the most with companies with 1K-10K employees. Those had interesting problems, interesting people, a sensible pace of work, and a somewhat tolerable amount of processes and bureaucracy. 50K+ employees almost always felt like I was in a satire. With really large companies (100K+), I came to understand how they could layoff 10% of the employees and still go on like nothing happened.
I'm not telling you to stay at your current job(don't stay at a job you hate!), but try to think about what you want your spare time to be like before make a move. Going to a place with a constant stream of challenging and interesting work might be nice at first, but after a while you might find your energy for side projects is zero.
There must be teams at the big 4 where you get the opportunity to do some interesting work and then go home and work on things that you are really passionate about. JSeymourATL provided a great answer - Assuming it is possible, network within the company and find a group that is doing something you find interesting. Unfortunately some companies are too political to be able to do this. Or you may have a horrible manager who will retaliate if you try to do this.
All that being said, some people need to be in charge. They need to be entrepreneurs. I know a brilliant engineer who owns a small construction company now because he'll do anything to not report to somebody else. He simply isn't built to have a boss and not have control of his work, or be obligated to VCs for a tech startup.
Your instincts may push you into a small startup where your work has immediate impact and feedback, but there's a space between 10 employees at 100K employees. I used to be in consulting (at a software company) and I worked with everybody from small startups that wanted to partner to companies with 200K+ employees. I tended to enjoy working the most with companies with 1K-10K employees. Those had interesting problems, interesting people, a sensible pace of work, and a somewhat tolerable amount of processes and bureaucracy. 50K+ employees almost always felt like I was in a satire. With really large companies (100K+), I came to understand how they could layoff 10% of the employees and still go on like nothing happened.
I'm not telling you to stay at your current job(don't stay at a job you hate!), but try to think about what you want your spare time to be like before make a move. Going to a place with a constant stream of challenging and interesting work might be nice at first, but after a while you might find your energy for side projects is zero.
There must be teams at the big 4 where you get the opportunity to do some interesting work and then go home and work on things that you are really passionate about. JSeymourATL provided a great answer - Assuming it is possible, network within the company and find a group that is doing something you find interesting. Unfortunately some companies are too political to be able to do this. Or you may have a horrible manager who will retaliate if you try to do this.
All that being said, some people need to be in charge. They need to be entrepreneurs. I know a brilliant engineer who owns a small construction company now because he'll do anything to not report to somebody else. He simply isn't built to have a boss and not have control of his work, or be obligated to VCs for a tech startup.