I'd take those reviews to heart. So many reviews these days are for promotional purposes and review items after they were just purchased. "My (fill in the blank) looks great. It was just installed." When multiple people take the time to write a review after having a true issue like cracking, I'd pay attention to it. Those real reviews are few and far between and really stand out.

I trust those reviews but there's also the fact that if someone has a bad experience theyre going to review it and complain. alternatively, those that have it and have no issues typically wont go back and leave a review saying so 5-10 years down the line

I have clients with Underscore and zero issues. No cracks no nothing, For one client it's been about about 8 years, with a teen boy who loved baths after crew/rowing practice.

Someone with a poorly installed tub might have "issues" but its been a no complaint for me.

The foundation for ANY tub, is important...and we never know in reviews with folks who never did anything "wrong" especially a DIY........let alone daily habits, what they may complain about up the road.

"

Alcove tubs, commonly made of fiberglass or acrylic, typically crack due to improper installation (lack of subfloor support), causing the material to flex under weight. Other primary causes include heavy impacts (dropped items), thermal expansion from extreme temperature changes, harsh cleaning chemicals, and natural wear. Here are the detailed causes of alcove tub cracking:

• Improper Installation/Lack of Support: If the tub is not properly supported underneath (e.g., without a mortar bed), it will flex when stepped on, leading to stress cracks, particularly in fiberglass models.
• Heavy Impact or Weight: Dropping heavy shampoo bottles or, in some cases, standing on the tub edge can cause immediate damage or create stress points that crack over time.
• Thermal Stress: Drastic, rapid temperature changes (very hot water in a cold tub) cause the material to expand and contract, leading to hairline cracks or brittleness.
• Harsh Cleaning Chemicals: Abrasive cleaners and bleach can erode the finish, causing the material to become brittle and, eventually, crack.
• Subfloor or Joist Failure: If the flooring underneath the tub rots due to leaks, the lack of a stable foundation causes the tub to sag and snap.

Signs of Trouble:

• Flexing: The tub feels soft or moves when you step in it.
• Spiderweb cracks: Often caused by heavy impacts, appearing as small, branching lines.

I would bet the install was not right if a tub crackes . I did read somehwere that a cement base was a good idea with acrylic tubs that are soakers I guess that would solve the issues .

Almost every tub made these days is acrylic and has been for more than 30 years. If the material wasn't successful none of the manufacturer's would be using it.

https://maax.com/bathtubs/all-products?selected=productlookups.installationtype.internal_value.Alcove

These tubs from MAAX can be order through any big box store.

It's more an exception to find tubs that are porcelain cast iron any more. The cheap tubs are enamel over metal. Those often go into multifamily housing units.

I have used Maax acrylic tubs for years for myself and client never had any issues