Strict rules: ritual - no, ceremony - yes
There are two ways to create holy water currently. The one you refer to in your question is the one from the PHB entry on holy water:
A cleric or paladin may create holy water by performing a special ritual. The ritual takes 1 hour to perform, uses 25 gp worth of powdered silver, and requires the caster to expend a 1st-level spell slot. (PHB)
RAW this option is not available for the sorcerer because they are not listed in the available classes. It is worth noting the the PHB was written before Xanathar's Guide to Everthing (in which both divine soul sorcerer and ceremony are found). So this may just be a case where the print has not been updated to reflect new class options or an oversight. Regardless, until an official clarification or errata RAW say no.
The other is the ceremony spell:
Bless Water. You touch one vial of water and cause it to become holy water.
This is a cleric spell, thus the Divine Soul Sorcerer has the option to take it. If they do, then they can make holy water! You mention this already in your question and the only reason I mention it here is because of the following.
Ceremony and the PHB ritual may actually be referring to the same thing
(Interesting point brought up by @PhilBoncer in his answer)
Note that both are 1 hour long, take a 1st level spell slot, require 25gp of powdered silver, and are both available by default only to clerics and paladins.
Seems like a pretty incredible coincidence right? Despite no explicit ruling confirming this, I think the evidence is pretty strong that both these things are talking about the same magic ritual which is now called the ceremony spell.
If this is indeed the case, then there is no conflict. The divine soul sorcerer can create holy water by taking the ceremony spell which would be the exact same way the cleric and paladin do it.
If you do not believe or accept this to be the case, keep reading and see why you might want to allow it anyways.
DMs should strongly consider allowing it despite strict RAW
DM all obviously have the right and ability to change anything about the game to suit their needs. But should they do that in this case?
Divine soul sorcerer backgrounds/flavor fits the ability well
Looking at the flavor text for the divine soul sorcerer, it seems that this could mean many different things depending on how the character wants to play their character.
Perhaps your ancestor was an angel, transformed into a mortal and sent to fight in a god’s name. Or your birth might align with an ancient prophecy, marking you as a servant of the gods or a chosen vessel of divine magic.
In some cultures, only those who can claim the power of a Divine Soul may command religious power. In these lands, ecclesiastical positions are dominated by a few bloodlines and preserved over generations.
All these fit very well with an ability to make holy water. In fact, the theme and flavor of them almost demand it.
The last example, in particular, is a compelling case for this. From a storytelling perspective it would make absolute sense for a "vessel of divine magic" in a place where "only those who can claim the power of a Divine Soul may command religious power" would be able to create holy water. It is a standard act of a divine actor to be able to do so.
The game allows the making of HW with a cleric/paladin spell, so why not the ritual as well?
The game already admits that the character has the right flavor and powers necessary to create holy water by giving them the ability to choose the ceremony spell. I don't see it as that much further of a leap to allow them access to the ritual as well (even if they don't choose the spell).
The risk of allowing this negatively affecting the game is very low
I don't see the ability to create holy water as having almost any potential to break any aspect of the game. The only things they could do with the holy water really are use it in battle or sell it. Both activities are done by other classes only rarely and without game-breaking effects. This isn't really any kind of significant power gain.
The benefit to flavor and roleplaying can be great
Allowing this ability can make the character feel more anchored to their divine heritage (whatever that might be) and could enhance roleplaying and create opportunities for backstory discussion and character growth.
So, if the DM wants to I think they can safely allow the divine soul sorcerer access to the holy water-making ritual. With almost non-existent potential for negative effect to the game and large potential for good aspects to come from it it actually seems like a very easy choice.