Building a road over unknown ground has been tried before many times. Logging companies do it all the time to get out the timber. They just drive a bulldozer through an area that has been cut and that is the road. But it is not a permanent road. Because to make a permanent road there has to be a good base so the road will not shift. A floor is much the same. If it is not braced properly underneath, or if the decking material is not level, then you will get all sorts of problems.
If the new flooring is going into the main living area and there is wood underneath the surface will be prepared according to the material you choose to put down. Old linoleum floors are usually a good base for more linoleum or carpet if they are in good shape and secured well to the old surface. If there are small patches of linoleum missing sometimes a flooring contractor 
will use a leveling compound.
This makes more sense than to try and scrape it off as the old glue may be rock-hard in spots creating a huge mess.
Tile is different. It should never go onto the original wood subfloor as the moisture may cause problems like squeaking and warping down the road. A marante or thin plywood board covering should be fastened on top of the subfloor. Fasten it down placing wood screws in grids of 5″ separation.
As well it should never go directly down on linoleum or old tile. This old covering should be removed or the mastic may separate and the tile come loose. Covering the old linoleum surface with plywood would also suffice but tile would have to be removed before the new subfloor went down.
