When a navy can afford battlecruiser specialization

Are fast battleships a better fit than battlecruisers for most countries?

Yes, unless a navy is large and wealthy enough to specialize; once battleships are fast, a distinct battlecruiser needs an even greater speed advantage.

A navy with limited resources benefits from ships that combine speed, armour, and battle-line firepower. Separate battlecruisers make more sense only when the fleet is large enough to afford specialized roles. As battleships reach 28 to 32 knots, a true scouting or pursuit type would need roughly 38 to 40 knots to preserve a meaningful speed margin. The category therefore depends on the performance of the contemporary battle line, not on a fixed label.