There’s also a saying in bike communities, along the lines of, it doesn’t get easier you’ll only ride faster.
Riding a heavy bike with no aerodynamics will lead to building strength faster. While it can be a bit frustrating if you’re new and riding in a group, joining more beginner friendly groups and upgrading the bike later is much better overall.
It is however really important to get the posture and pedaling technique right. Way too many people in expensive gear do push-only instead of a push-pull. That’s like biking 101. It’s much better to get that smooth pedaling and core support. It’ll prevent injuries and fatigue.