I set up SPF, DKIM, DMARC, not on any public blacklists (confirmed through https://multirbl.valli.org/), whitelisted by DNSWL.org at medium trust level, never sent any bulk email, and I had constant deliverability issues with Outlook and Gmail. Both of our experiences might be true, but yours does not invalidate mine. Simply setting up SPF and DKIM is not sufficient to ensure deliverability.

It still happens to me from time to time, and Postmaster tools don't help either (honestly what more do you want from me Google!)

I'm still refusing to give up the good fight.

I had both setup previously and constantly ended up in my recipients spam. When I'm trying to sort my life admin with local council/government/landlord/utilities, it's one thing to have a 'cool' custom email, but it's another to say "oh yeah, sorry, it's probably in your spam".

Haven't had an issue since I moved to 365. Costs a little more but so much less hassle. I don't like it but I also need people to actually receive my emails.