The case for boring
Cards like the Citi Double Cash, Wells Fargo Active Cash, and Fidelity Rewards earn a flat 2% on everything: no categories to track, no caps to monitor, no annual fee.
For a surprising number of spending profiles, a single 2% card captures 85–90% of the rewards a carefully tuned multi-card setup would earn. If your spending is spread thinly across many categories — a little dining, a little gas, a lot of "everything else" — category bonuses have little to grab onto.
Where flat rate loses badly
Category cards pull ahead when your spending is concentrated:
- Heavy grocery spend: 6% (Blue Cash Preferred, capped) or uncapped 3–4x beats 2% by $120–$400/year at typical family grocery budgets
- Heavy dining: 3–4x dining cards out-earn 2% by 50–100% on that slice
- Rent: a flat 2% credit card usually can't touch rent at all without fees; rent-earning cards exist specifically for this
- Travel booked through portals: 5–10x portal rates dwarf 2%, when the portal price is competitive
The pattern: each concentrated category is worth roughly (bonus rate − 2%) × annual category spend. One or two strong categories can fund an annual fee and then some.
The hybrid answer
The best setups usually look like: one or two category cards covering your biggest concentrated spend, plus a flat 2% card sweeping everything else. The hard part is choosing *which* category cards — caps, fees, and overlapping bonuses interact in ways that per-category comparison tables can't capture.
That interaction problem is what the optimizer solves exactly: it routes every dollar of your actual spending across every candidate combination and proves which setup nets the most after fees. Sometimes the answer really is "just use a 2% card." It's nice to know that for certain instead of wondering.