Depends how professionally (or realistically) you want to play?
Plywood/MDF/Hardboard under the felt just won't play the same, it's sluggish and totally wonky on your hits and masse.
Speaking from experience, playing on a "fake" pool table without slate is the absolute worst thing ever - like basically you might as well NOT play on it because it's not enjoyable, nor is it helping you practice; in fact quite the opposite, it HURTS your league game. Husband and I were on a team some decades ago so we'd bought a used full size table to up our game on the bar size tables we did tournaments on, it was so terrible to play on that we only had it for a year [of near constant fiddling, leveling, and attempting to stabilize/sturdy up the field] before getting rid of it. At first we thought it was the table just being junk, so we bought another "highly recommended" 7 foot "fake" one new in box thinking the deflection across the length wouldn't be as bad, but it was actually worse than the 10 footer!
You could just buy the slate, and a decent quality felt, but I think that's the vast majority of the cost of the table so...