Gregory's Server
Yes, Gmail absolutely makes it difficult to get reliable delivery to Gmail users if you're not on Gmail or one of the other big webmail providers.
My server has never sent spam, ever.
It's had the same IP address for 15 years.
It's not on the DUL or any other list.
It is properly configured for and uses SMTP STARTTLS, DKIM, and SPF.
It has restrictive policies for SPF and DMARC and advertises as such.
It passes all validators.
And deliverability to #Gmail is a complete crapshoot.