Granted, I'm also super lazy, but Finnish and Estonian should be close enough to just have some threshold to get over until it's pretty smooth, I guess?
Fwiw, I'm native in Swedish, but I speak and write Finnish daily.
To go on about my earlier comparison, I can really visit the site for a Danish or Norwegian Bokmål newspaper like Politiken ( https://politiken.dk ) or Verdens Gang ( https://www.vg.no/ ) and start reading with a feeling of just moderate confusion. Academic text would require some extra effort. The "voice in my head" or mode of reading doesn't really even change, because I've never attempted to communicate in either Danish or Norwegian per se.
For Estonian Postimees (https://www.postimees.ee ) I'm stuck pretty much immediately. I can pick up words and some context, but that's it.
At my first job, at an internal IT Service Desk for a certain Nordic energy company, I dealt with Norwegians and Danes. But it was a business context where everyone just seemed to agree to just make a polite effort at having a maybe slightly "clear in a Swedish way" common Scandinavians language, because switching to English would feel a little silly. I guess some of the older dudes working in the field somewhere in Norway might not have spoken English.
Many words in standard Estonian do have true cognates in Finnish, but the Finnish counterparts have a slightly different or more specific meaning, or are nonstandard or colloquial. A typical example would be maja which in Estonian means "house" or "building" but in Finnish has the more specific meaning of "hut" or "cabin"—a dwelling more rudimentary and temporary in nature.
EE: ära surra (to die) - FI: surra (to mourn)
EE: vaim (ghost) - FI: vaimo (wife)
EE: kannatus (suffering) - FI: kannatus (support)
EE: pulm (wedding) - FI: pulma (difficult problem?, puzzle)
But anyway, there we probably have it, your vacations as a child. No lifehacks can beat exposure to language at a young age, I guess. SAD.
Waiting for the day when some drug can trick the brain into some semblance of a kid's language learning skills.