I think most solo players understand and accept the limitations of solo play in terms of high end rewards and contents specifically designed for groups. Most folks don’t want epic rewards for which others raid and do mythic progressions.
However, what solo players want is content they can do solo, or casually, which is fun and rewarding, and does feel like a progression. As with all players, soloers want to feel that their characters do get stronger, and life gets a little easier as they progress. Sololers don’t want to be excluded from the major features of the game, except for the specific group content (see above) Unfortunately, that has not always been the case in this game, since on several occasions, even open world PvE, perhaps the only quest content soloers can actually do, has been tuned for groups, and there are, indeed, hard to kill mobs out there who drop literally nothing worthwhile.
Again, the majority of soloers don’t want mythic dungeon or raid drops, but it would be nice to keep Open world PvE solo-centric, keep professions soloable until the upper-tiers, and not gate normal open world PvE behind dungeon and PvP content.