The player profile you posted shows that MIT player is a UTR 10 - which means he is a very high level player. I’m not sure why that player isn’t ranked, but it possibly has something to do with him attending a boarding school. Most tennis recruiting starts the summer after sophomore year but the players have most likely been on the coaches radar much earlier than that. One superstar at my son’s tennis academy had college coaches scoping him out at national level tournaments when he was in middle school.
As far as MIT is concerned, they do not really take athletes that are not otherwise academically competitive. One of my son’s best friends who was a two star recruit and a UTR 10 or 11, ranked in the top 10 in Georgia was in contact with MIT’s coach and told he needed at least a 3.9 unweighted and 1500+ SAT. My son has a friend who was recruited for another sport at MIT and currently attends. That kid was class valedictorian,3 time aime qualifier and USACO platinum among other off the charts academic achievements.
If you are truly a high level tennis player, you certainly can email a few coaches. Do you have a UTR rating? Are you playing no. 1 singles at your school and beating top tournament players? There are not many walk ons in college tennis. The rosters are very small - it’s not like larger sports such as football or swimming. Even if a school might consider you as a walk on, that will not give you a boost in admissions. If you truly want to continue playing tennis, club or intramurals are available most everywhere. My son plays club at his school (a D1) and there are some surprising high level players who just didn’t want the time commitment involved in varsity athletics.