I've always thought that literally anything that gets you to the end is a valid strategy. A player can be accused of floating or latching onto a big player, but if they stay below the radar and don't annoy anyone too much, good for them!
Ashley may not have won many comps, but she said in her final speeches that she did, in fact, have a strategy that kept evolving as the players were evicted and the game changed. She tried to be likable, but not too likable so she wouldn't be viewed as a social threat. She sought out strong players who would protect her, then looked for others when those protecters were evicted. She methodically worked her way through the game while mostly staying off the block and not causing enough contoversy to be strongly targeted. She kept her cool at the end and won the final HOH, then chose to evict Morgan knowing she couldn't win against her. She did a lot of strategic planning as the game went along. She just wasn't loud about it. That's what made her successful.