The problem with DDO right now is that SSG chose to extend the wrong axis of potential play for all players.

Along about 2015 they had a problem with the existing player base burning out on a few basic repetitive grinds. They had heroic lives and epic lives as the main grinds and the dedicated player base was ripping through those fairly quickly. Iconic lives were also being expended by the people who really wanted to grind for endgame. The answer from the viewpoint of the devs was to add more grinds for the players who wanted to grind alongside periodic content releases, especially high level raids, for those players who wanted a brief endgame experience and validation of all the grinding before diving back into the grind.

For most people the effect of the choice that SSG made was to sideline alts and work on their main, with maybe one alt as a change-of-pace left at cap to do the raids. The meta shifted endlessly with power builds promoted in a mostly pay-to-acquire mode. For the grinders the power builds created an even faster-pace of power accumulation. The ceiling moved progressively upwards and people who were not power grinders and who had less time to play were gradually marginalized in terms of keeping up with the grind.

One of the problems with the endless grind meta was that people wanted more power and a faster pace of leveling to make the grind seem both worthwhile and productive. Enter Reaper mode which provided both power creep in the form of additional health points not available in any other way and also a faster pace of grind through the existing processes.

This produced an inevitable split in the player base, with less dedicated players continuing to grind along the pre-existing pathways while the dedicated daily players switched to Reaper mode and began that grind. New players got caught in the crossfire as there were far fewer LFG's for non-Reaper groups and the new mode was not new player friendly at all. The grind became really oppressive at this point for most players.
Then SSG added racial past lives and completed the transition to a Methuselah meta. There were so many potential past lives at this point which cumulatively added so much power that a new or more casual player could not even find a reasonable pathway to a "complete" build.

Then items were nerfed across the board, leading to a significant power loss for players who were not grinding hard. Then Epic Destinies were reworked adding another grind and rewarding players who had many Epic past lives in the process.
At this point the game is no longer approachable as a new player or a player with less hours to play. There is no reset point with each expansion. There is no reason to begin an endless grind. All the potential of the game, which is considerable, is wasted except from the standpoint of a dedicated player who is already well advanced in the grind.

So let me explain why I think the axis of potential play was the key element in moving DDO forward and maintaining it as a viable game for the average player and specifically the new or casual player.
If SSG had chosen to extend the game horizontally instead of vertically they would have taken all the assets they put into the new systems, of which there have been many, and instead devoted them strictly to new content. That content would have been in the form of new quests, expansions, raids, classes, enhancement trees, iconic characters. There would have been new stuff to do on a quarterly basis. Much of the new stuff would have been gated behind the store, paid expansions or VIP access.

Content would have gotten gradually harder as new content was added. This would have been a necessary addition to the game to keep veteran players interested as their gear improved quarterly. Most of the difference could have been in raids and specific gateway quests into those raids. Nobody complains when new gear and content is added. That's a healthy addition to a game that does not discriminate against newer and more casual players. It is not as easily attainable by those groups but they have a pathway to gain it without dedicating their lives to the game.

A new player looking at the game right now would see a game stretching to the horizons instead of to the heavens. There would be a pathway for them to join and prosper. Much of the horizontal content would be optional as the newer content packs, expansions, enhancement trees and classes would be more powerful than older content. There would be great incentive to purchase the last few expansions and the content released around them to get as near the power curve as possible.

This would have been the DDO that had relevance to all but the most dedicated players. It's the DDO that would have a fighting chance at growth over time instead of inevitable decline.
Just as a side note: you've got your dedicated players as an almost captive audience for various reasons. They are not the people you should be spending most of your time on retaining. It's the newer more casual players who would normally vastly outnumber your dedicated base that you should be spending time on.

I spend much less time and money on DDO than I used too. I have very little incentive to change that pattern at this point. The content for the most part is worn out for me. The ceiling is *much* too high to seriously contemplate grinding towards in a 15 year old game. By much too high I mean the thought of grinding that much is nauseating in the extreme. I spend time in multiple games and none of them have put this kind of grind in front of the player base. That's why I spend my time and money there instead of in DDO.