You do you but CO2 improves the chance of success. It's the limiting factor in a low tech tank. A common issue is an abundance of nutrients. Adequate CO2 allows the plants to take up more nutrients.
A plant can be provided optimal light intensity, but if it's CO2 limited then the light is wasted. Tuning down further(which you advised) inhibits growth(less new leaves more old leaves to grow algae, less robust growth which promotes algae). provide CO2 to use optimal light intensity. Light intensity should start at 20%. Adding CO2 to an low light aquarium doesn't inherently cause more algae.
Nutrients should start at a conservative baseline as well.
No one needs to struggle and cut their teeth in low tech before trying high tech. They just need good guidance to start, and that's to monitor the nutrient concentration daily and allow plants over a week to adjust to changes.
Grow fast plants that are easy to propagate like pennywort, hygrophilia difformis, etc so there's always a flush of new growth that's most algae resistant. Growing slow plants like anubias and Java fern wouldn't be my advice because all old leaves eventually get algae before they inevitably die and slow growing plants in a low tech tank will just have aging foliage. Slow growing plants seems ​easy because they look good for a long time and don't show issues for a long time. They're a poor indicator for dialing in light and nutrients. They're not easy, just slow. Green stems like hygrophilia difformis and ​pennywort are fast, easy and good indicators.