There are more options than ownership or not riding at all; it doesn’t have to be either/or. You don’t have to own a horse in order to ride, or keep buying more if one gets injured. Some people don’t buy a second horse and wait for their one-and-only to recover*. Or sell/give away/put down/find somewhere super cheap to retire (if possible/doable), before they can buy another one.
That said, I don’t currently ride in part because I can only afford one horse, who is on retirement board. But if I really wanted to, I could take lessons somewhere or find a horse to lease. It just hasn’t been a priority for me recently.
*If you have a trainer, you could convey your willingness to ride/hack horses that are riderless. If you’re sufficiently competent as a rider, most trainers I know welcome having the extra (free) help. If other people know you are willing to ride, and are good at it, and care well for the horses, it builds connections and you may end up knowing someone who is willing to offer cheap(er) pasture/retirement board, or has horse that needs riding, or the right one to lease who can match your riding goals. Leasing, as mentioned, is also a viable option and may be preferable to ownership if this worry is surpassing your enjoyment of having a horse or two.
If your horse ends up serviceably sound, but not up to the level you’d like to ride at, you could find a lease for him too; you’d retain ownership and have control of how he ends up, but it would temporarily lighten your bills on him. Even a “free lease” where they pay you no lease fee, but pay for all horse’s expenses, might be a situation to look into, given the right person and if it frees up enough funds for you to continue riding.
Also, if you have multiple horses getting injured in similar ways, I’d look into the management of the horses and facility. When we moved from first boarding barn/trainer to second, injuries still happened, but less frequently/severely – we also knew more about horses as time went on, but there was a lot not quite right about the first place that we didn’t realize (that point when you don’t know yet that there’s a lot you don’t know) until we were away from it and experienced different management/training styles.