A stretch inherited IRA is actually a super awesome thing to have, so you definitely want to speak to a rep at Vanguard before blowing it up and trying to take it all out to invest in other formats. I would cease any and all communications with the current agent and definitely stop considering any of their advice. They've treated your account as a money pit for their company, so get the facts on exactly what you're holding with them and then speak to Vanguard to get all the options. (I have a substantial iIRA and use it as my main source of living expenses now since I'm completely FIRE, so I do understand how this all works, so it yours is lousy, it is ONLY because of who you have it invested with, not the account itself)
The advantage to an iIRA is that it is a tax deferred account, BUT you can take distributions on it at any time with no penalty. This is a Very Big Deal.
And you're being told some things that are flat out wrong, or else are related to the particular company you're invested with, not things that are typically associated with an inherited IRA. You are able to take out any amount from a regular inherited IRA account with zero penalty, you just will need to pay whatever taxes are owed, based off the amounts you withdraw and your taxable income bracket for whatever calendar year you do the withdrawals. If your agent/company has imposed limits to your account for withdrawal, that's strictly on them. (agree with mary w - it may be they put you in an annuity which could impose limits according to their own rules)
Yes, you have to take a required minimum distribution every year, and yes, you may have to pay taxes on it (in most cases unless you are very low income/taxable bracket). But the ability to grow your investments tax deferred in an iIRA without taxable events UNLESS you withdraw, and even then can draw down at any age penalty free... that's a great combo.