Retiring the Quantum Capsules might backfire
Removing the Quantum Capsules could have the exact opposite of the intended effect.
I don't know what the idea or reasoning behind the initial release of the MUFG Capsule was but the Quantum Capsules have worked as somewhat of an equalizer. Many Agents living in rural areas don't have access to high-level Portals, even more so now that each Agent can only deploy a single L7-Resonator per Portal again, preventing two-Agent-teams from creating Level 7 Portals. Sure, as a Level 8+ Agent you still get the occasional L8-Resonators or L8-XMP Bursters from Level 6 Portals every now and then but it's not enough to sustain active gameplay which means that if you play Ingress in a low activity rural area as it's supposed to be played, on foot, the retirement of the Quantum Capsules will be a big blow.
There is a group of players however who will not be hit nearly as much: "Cargress" players; those people who use their cars to drive from Portal to Portal to hack, link, field, capture and destroy. For them a lack of high-level items virtually doesn't exist because if they run low they'll just jump into their car, drive to the next Level 8 Portal, hack it until it's burned out and repeat that process until their stocks replenished just to then descent upon those rural Agents with overwhelming force which, if those rural Agents don't have other active Agents from their faction around, can take them months to recover from.
Quantum Capsules have worked as an equalizer in that regard. Even those Agents that don't have the luxury of having a Level 7/8 Portal within normal reach (2-3 km radius) are able to get decent numbers of high-level items (XMP Burster, Ultra Strikes, Resonators, Power Cubes) to defend themselves from attacks as well as regain and rebuild what they've lost reasonably quickly.
The argument for retiring the Quantum Capsules seems to be that they allegedly cause Agents to be lazy and sit at home only using Quantum Capsules as their source of items instead of walking around hacking Portals, fulfilling Ingress' moto "It's time to move" but I would argue that even if that might be partially true in some cases, removing the Quantum Capsules will not resolve that issue instead expediting it, because the advantage of those "Cargress" players over rural, walking Agents will be even larger.
Since the 26th of December 2016 Quantum Capsules (then still MUFG Capsules) are no longer able to reproduce Very Rare items, which is a good idea since if Agents want to get those top Portal Mods for example they have to go out and hack a large number of Portals. The addition of the rare Kinetic Capsule on the 14th of September last year was a great idea and complements the equalizing effect of the Quantum Capsules quite nicely since those who play Ingress as intended, especially those in rural areas, now have a way (which isn't available to "Cargress" players) to get their hands on top items by refining the rare Portal Mods they have gotten through hacking and the Quantum Capsules into the very rare versions of said Mods by doing what they already do best: Walking and really living up to the moto "It's time to move".
The use of Quantum Capsules and Kinetic Capsules in concert will get Agents to walk around more as it gives them a true gameplay advantage. If the Quantum Capsules are removed however the scale will move back into the direction of those who use their cars instead because them driving from one high-level Portal to the next can overpower the beneficial effects of the Kinetic Capsules since one still needs (rare) items to start a Kinetic Capsule-program and if you have fewer Portals around and take more time to get from one Portal to the next you are still at a clear disadvantage to those who simply choose to drive around.
Conclusion: Considering everything laid out above I would suggest to retain the Quantum Capsules and to expand the range of Kinetic Capsule-programs (e.g. break down Force Amps into L8-Ultra Strikes and Turrets into L8-XMP Burster) to award all the walking Agents out there and give them a fair chance against those people who choose to drive instead.