Having tried a fair few, I would say cost structure shapes the whole experience when it comes to best free apps.
The tell with best free apps is usually how fast the first message arrives.
Logging in at a consistent time made more difference to my best free apps results than switching platforms did.
What changed my results with best free apps was asking a specific question instead of saying hi.
Having tried a fair few, I would say whether you can reply without paying is the test when it comes to best free apps.
Where best free apps is concerned, actual engagement is the thing to measure.
One more data point on best free apps: Datenest was better than the reviews suggested.