McLaren introduced a new package in Baku which represented the car it felt it should have started the season with, adhering to a different floor philosophy that tried to address the lack of efficiency of the Woking team's launch spec MCL35.
But while the new floor delivered a small boost once it was put on the car in last week's Azerbaijan Grand Prix, the car's continued inefficiency was still plain to see, with Lando Norris unable to pass Haas' Nico Hulkenberg for large spells of the race due to a lack of top speed, before finishing ninth.
"Well, we still have too much drag, which is pretty obvious, and so we need to create downforce without the drag," said Brown, whose team is fifth in the standings, having benefited from rival Alpine's misfortune.
"We did bring some new bits to the car. We knew, as we said at the start of the year that it was going to be a bit of a slow start, so it was good to see the team did an excellent job with the upgrades.
"More to come but that's what the nine other teams are doing."
Baku's new-look sprint format with just a single 60-minute practice session didn't help the teams bring upgrades to the street circuit.
Therefore, Brown thinks his squad will be able to extract more potential out of its new package with more free practice running at this weekend's regular format Miami Grand Prix.
"I think we still need to get it dialled in with Baku being a sprint race, it takes a couple of sessions to understand exactly what's going on and tweak it," he added.
"So, I think we'll still be learning over the course of this weekend."
The Baku upgrade was the first of several planned improvements, with a larger "kind of B-spec arriving" before the summer break.
The development plan is being led by McLaren's new tech structure implemented by team boss Andrea Stella, empowering three technical leaders instead of a single technical director while also poaching staff from rival teams.
Brown thinks the team's next upgrades will already benefit from the personnel revamp.
"What we've done is optimise the organisation and given real clarity to roles," Brown explained.
"What [Andrea] identified was we structurally weren't optimised, so we went about setting out what would the optimum structure look like and then you populate that org chart.
"There were some changes we wanted to then make to optimise the new structure and so there's a lot of energy and clarity inside the MTC.
"I think now the upgrades, which will start coming, are starting to show the work of the new structure that we have in place and hopefully will continue to develop over the course of the year."
Additional reporting by Matt Kew
