Why you should keep investing in a 401k: I'm not American, but from what I've read, those are tax advantaged accounts. Max out tax advantaged investments before you invest in after-tax accounts, for the very simple reason that you avoid paying taxes on that money and instead get to invest it. Even when there are certain legal limits to these accounts, the avoiding of paying all that tax is almost always worth it.
You say you don't feel rich aged 25 making $200k/year. In what kind of environment did you grow up? For reference, the median income is about $45.000 as far as I know. If you're making $200k/year aged 25 (at the start of your career, not at the end) that puts you at the very top income levels of the wealthiest country in the world, without any student loans, that means you're extremely rich. I don't know if FIRE is your goal, but at this income level you could definitely FIRE in a few years if you wanted to.
To give you a better advice, I think it would be helpful to know your goals. You're 25 years old and apparantly succesful in your job. You don't mention a long-term relationship or spouse, so I'm assuming marriage and kids is not on the cards right now. I can imagine you might not want to retire anytime soon at all, but you don't have to pursue RE to want to reach FI. But maybe you are tired of the rat race and in that case, you could achieve that in a very short period of time.
If you're just thinking about FI while pursueing your career, the easiest way to achieve it is to invest all the money in your vanguard accounts. You don't have to do anything except transfer the money on a regular base. You can just go on with your life and career and your money works for you until at some point you're FI and you're free to keep on working, or not.
If you're also thinking of RE, getting out of your current job at some point in the near future, other ways of investing that require a lot more work, like flipping houses or becoming a landlord, come into the picture. Do you have any DIY skills? I know flipping houses looks easy on TV, but we bought a fixer-upper a few years ago (not to flip, but as our family home) and believe me, it's a hell of a lot of work. With the kind of income you have, I'm assuming you have an office type job and lots of professional skills, and likely work some overtime too. Do you have the DIY skills and the time to make this work?
At your age, if you have the skills, you can probably find the time and the energy to flip a few houses or to fix them up to rent them out, but as a permanent side hustle I think this would be hard to combine with a full time, demanding job in the long term, especially if at some point you would marry or have kids. So I think this kind of path would be more advisable if you're planning to RE at some point. This is what MMM did himself too. I think this is also much more of a 'hit or miss' investment than the stock market is. You can make a lot of money in a short amount of time, but there's also a much bigger chance of losing money in the short term. You might need to hold on to certain properties for a very long time until they are profitable because of circumstances that are beyond your control. This happens with index funds and stocks as well, but those don't drain all your energy and money to maintain. They just sit there in your account until they've regained their original value. You don't have to pay property taxes, repair storm damage and replace leaky roofs, not to mention pay lawyers to kick out bad tenants.