That uh, defeats the purpose of a Raid. The difficulty of a Raid comes with multiple players working together toward a collective goal. Everyone has to contribute and success is measured based on everyone performing their parts.
This can at times be very frustrating when you perform your part, but other players do not perform theirs resulting in a failed attempt. Now, different levels of forgiveness can be added to allow for some failure and it cab be designed so that players with very high skillsets can turn the tides when multiple players die.
A soloable “Raid” functionally no different than a NMD Dungeon with a Boss at the end or an Uber Boss with better mechanics. You can only make these encounters so challenging because you are only dealing with a single player in mind. Scaling it up to arbitrarily be more difficult with added mechanics for more players present is, well, kind of dumb.
If you want to see content that is sort of tuned to Solo play, check out the Spire Towers of Lost Ark. You COULD solo Guardian Raids also, but it depends on the Raid Boss and you typically have to well outgear it to reach that.