If your employer offers a 401(k) plan, you can still open a retirement account at Wealthfront and contribute up to $5K a year (the legal limit), but contributions will not be tax deductible, so you're generally better off contributing to your lousy 401(k) plan... especially if your company matches contributions (an instant 100% return). That's the better choice even if your 401(k) underperforms an alternative investment by 4% a year for 20 years in a row.
Chances are you won't be at the same company for 20 years, though. So when you leave the company, just roll over your 401(k) account to an IRA. You can do that many places, including Wealthfront. Your 401(k) isn't very flexible, and that's by design: it's constrained by the agreement between your employer and the institution providing the 401(k) plan (which also typically provides the underlying investment products).
If your employer doesn't offer a 401(k) plan, then you're eligible to make tax-deductible contributions of up to $5K ($6K if you're 50+) to an IRA (opened anywhere you like) each year.
Regardless of how you choose to invest for retirement, if you're lucky enough to be accumulating more than you care to allocate to your retirement years, you may want to consider opening a standard personal investment account (taxable) at Wealthfront, Vanguard, or whatever institution you fancy.
Hope this helps!