What I find interesting is the impact of advantage on success probability and how the intersection of skill and tool proficiency potentially guides character and party composition as well as general gameplay strategy.
For instance, if most parties want to include a PC with lockpicking ability, the default assumption historically has been someone with thieves' tools proficiency, decent Dex, and (ideally) expertise. The virtual certainty now that you can have advantage on checks (by having proficiency in both sleight of hand and thieves' tools) disrupts those assumptions.
Here's a probability of success chart, assuming 17 ability score and +2 proficiency bonus:
Looking at this through a 2014 lens, one would observe a linear improvement by adding proficiency and then adding expertise. If a party wanted a >50% chance of picking most locks they were likely to encounter, expertise would be the best bet (short of having multiple proficient characters).
Adding advantage to the mix really changes things. Looking at the DC 15 column, we see that a PC without expertise but with intersecting proficiencies has a significantly greater chance of success than a PC with expertise but no intersecting proficiency. Adding expertise on top is nice, but not as impactful as getting advantage.
So that arguably diminishes the strategic relevance of expertise as a class ability, but it also points to a new paradigm where searching out -- and presumably convincing the DM to allow -- intersecting skill and tool proficiencies is a key gameplay strategy due to the sizable impact of advantage on success probability.