Durrell Berry opened the scoring midway through the first half with a well-taken finish before AFC Wimbledon’s Jack Smith levelled shortly before half-time.
Despite heading out of League Two, Johnson has confirmed he will stay on next season and the Robins manager knows what needs improving.
“I needed to have a look at the lads and see which ones are first-team material and have enough of a game to make sure we’re in the top few of the Conference next year,” he said.
“We need that quality to score more goals and I’ve seen that since I’ve been here.
“To succeed in the Conference you need to score 90-plus goals and recruitment is key.
“Every game you learn something new about somebody and some of the lads have got a little bit more experience.
“It’s going to need a pretty big change around over the summer.
“It’s important to get the right players in, we need those who can affect games, with both goals and assists.
“I’ve identified some of the players I want to bring in and next week we’ll tell the squad who won’t be here next season.
“It’s important to try and do our business early, I’m looking forward to the summer, it’ll take a lot of hard work, phone calls and speaking to old friends of mine. Hopefully I’ll be able to call in a few favours.”
AFC Wimbledon have limped over the line as they finished 15th after failing to win any of their final eight games, leaving boss Neal Ardley also searching for goals.
“The result sums up our season, the chances count was way in our favour, but we just can’t finish them off,” Ardley said.
“We gave away a sloppy goal and after that you’re chasing the game, but we could have had four or five.
“Ultimately football is won by what happens in the box.
“We know where we need to strengthen and what players we need.
“Trying to find that quality of player that fits our profile isn’t always easy, but we’ll work hard at it.
“I know if we have a good six weeks recruiting. We’re going to have a lot of good weekends next season, so it’ll take a lot of hard work, but I’m looking forward to it.
“A striker is on the list. While I can’t take responsibility for the players missing the chances, I need to find someone who can get us those goals and that could be the difference.
“I don’t think I’m being bias, but if we had got what the performances deserved in games this season, then we would have picked up at least another 10 points.
“I haven’t seen a team come to Kingsmeadow and be better than us since January, but we know where we need to improve and that’s football.”