Toboggans

Boats, as of 1.16, can slide along ice ways at great speeds, and using the nether can reach incredible distances within a short amount of time.

However, this is quite nonsensical, however fun it may be, and also has lead to many issues regarding a lack of control with said boats, and so I have a solution.

Toboggans! Toboggans would be a good replacement for this mechanic, whether the mechanic was intentional or not. You could make the toboggan more expensive than a boat, costing iron, wood and maybe wool.

The toboggan's sole purpose would be to slide along surfaces, meaning the max speed you can achieve is inversely proportional to the friction of the block (Something like soul sand would be really slow, and effectively pointless, but blue ice would be like a drag race)

The toboggan would slow down if the direction it's facing is perpendicular to the direction it's moving (The amount of perpendicularity would change the rate at which it slowed)

It may also have good handling as to make junctions on ice ways more plausible, however that may be implemented.

An extension to the idea would be to stitch multiple toboggans together to make a longer one. Two people in a boat has often caused problems for parties of 3, so why not make a toboggan with 3 players inside! 3x the awkwardness, and 3x the laughter.

The propulsion of toboggans in real life is gravity. Due to the fact that Minecraft is primarily meter cubes, smooth slopes aren't exactly feasible. However, fireworks are feasible.