There are 2 ways to accumulate enough stocks to FIRE:
1) Accumulate shares whose current market value is enough that you could sell them and buy bonds, REITs, etc. and cover your living expenses. This was the proper strategy to execute if you hit your FIRE number in 2000 tech stocks or in 2017 cryptocurrencies, etc. Call this "bubble exploitation strategy".
2) Accumulate control over enough corporate earnings to exceed your living expenses. Arguably, once you've hit this number (EPS -corporate waste - taxes - fees = spending) you are FIRE'd because those earnings are being credited to your wealth in the form of buybacks, dividends, or growth. If VTI went from around $130ish today to $20 tomorrow in a computer-driven trading panic in which earnings weren't affected and even if it stayed there for a year, there would be no need for a person with 10,000 shares to get a job, other than to buy more shares or avoid selling. Despite Mr. Market's panic, the EPS of those shares is the underlying revenue stream supporting their owner's FIRE lifestyle. A simplistic way to understand this is that the dividend would still be there. On further reflection, buybacks and growth are contributing the same or more to the owner's wealth despite the lower market price. The market value of that earnings stream will certainly recover and the owner of the earnings stream will be a millionaire again someday. Call this the "earnings accumulation strategy".
To get to the question, a price correction is bad if it interrupts a person pursuing a "bubble exploitation strategy" because they missed the chance to purchase more reliable earnings with proceeds from bubbling assets. A downturn is always good for anyone pursuing FIRE with the "earnings accumulation strategy" because they can start accumulating earnings streams on the cheap.
You'll note that the good/bad perceptions apply to the same situation, are subjective, and are completely related to strategy. That's the point.
When you get to FIRE you have a basket of wealth-accumulating shares bought over X years at an average price of Y per share earning you $Z per year which you accept as dividends, interest, unrealized capital gains, or realized capital gains. The numbers do not remember the messy history of how they got there. The shares do not remember how you came to own them. Whether you exploited a bubble, won the lottery, or maxed your 401k for 18 years only matters in terms of time to FIRE. Time to FIRE is mostly a factor of savings rate, but is also affected by the sequence of market returns - a factor that is completely unpredictable and not worth much consideration unless you think the "bubble exploitation strategy" is the only way to win the game.