The "core" or "foundation" rules and principles of deck building have not changed with the ban of LTC, IMO. Afterall, many, many decks were constructed for years before LTC was ever released, and deck building will continue after the LTC ban date. IMO, this is just another step in the game's evolution. Players' deck building will just "evolve" again or adapt to the fact the LTCs will no be available for use June 15th and after.
LTC was just 1 card in my decks. My first "reaction" to LTC's ban (I've already modified my current decks) was to simply replace it with a Sacred Ash in order to recover and recycle discarded Poké. At this time, recovering energy and Supporters are less of a concern right now since there are other available Items, Poké attacks, etc. that can recover these resources. Another viable option I plan to test is the Bunnelby (PRC 121) which can also recover and recycle discarded resources.
The biggest impact I've experienced has more to do with my game strategy. Deck resources management has again become much more critical. One can no longer rely upon an LTC-like card to completely replenish deck resources for re-use, counter certain decks, prevent decking-out, etc.
The LTC ban also "limits" (eliminates, most likely) my utilization of certain deck "engines" that "speed" through one's deck T1.
Lastly, the LTC ban also impacts deck choices. For example, prior to the ban, I would not have expected to encounter certain decks at the upcoming Nats tournament. Now with the LTC ban, some decks (e.g., Night March) have become quite viable again.