Not many players left, which is well deserved. Here are a few ideas on how to improve the standard format substantially, before the last thousand real players that are left quit.
-Make clear class identities, there should be a reason that 11 classes exist. Not just for flavor but for actual gameplay purposes
-Back to the first point, each class should not only play different but also reward different skill levels of the player piloting them. You want an easy accessible beginner friendly class? Play Paladin. Want a high skill ceiling limit testing class? Play Rogue. Etc
-Mana matters again, and so does the stats of a card. If a card has a battlecry there should be a bottleneck in stats. If a card is purely stats but with no effects it can compensate with cost. The problem is when both are (not) present.
-Counterplay needs to come back. Theotar were an excellent card which offered very good counterplay. The problem lied with too little disruption/counterplay options were available, therefore everyone ran theotar to prevent getting counterplayed.
This could be prevented if more options were open. More ways to counterplay and play a mind game back and forth. This would also allow cards to be powerfully designed but with a delayed effect so that it could actually be countered.
-Reduction of yearly expansion format from 3 to 2, but with betas beforehand and a larger new card pool.
A select few players would be invited before each beta to have enough time to test cards and their interactions before the expansion would be released. Feedback and communication could be as simple as a private forum between the devs and testers.
If the meta would be too stale as a result from this then mini expansions could drop each season, of course with a different acquiring method than we have now, otherwise it would be impossible to keep up.
-Guilds and social features. Make it more lucrative to log in and interact with each other. Friendly guild battles and multiple social features, spectate and share previous matches.
-More ways to unlock cards. Weekly/monthly chests that players would grind in order to unlock different tiers of cards. Easier for new and returning players to catch up.
-More ways to monetize the game through cosmetics. Custom boards (legends of Runeterra). Custom hero power art portraits. The possibilities are endless without alienating the remaining player base.